Tone down verbosity of BackupManager logging

INFO  - 2017-11-07 22:25:43.812; [   ] org.apache.solr.cloud.BackupCmd; Starting to backup ZK data for backupName=test
INFO  - 2017-11-07 22:25:43.816; [   ] org.apache.solr.core.backup.BackupManager; Writing file managed-schema
INFO  - 2017-11-07 22:25:43.820; [   ] org.apache.solr.core.backup.BackupManager; Writing file protwords.txt
INFO  - 2017-11-07 22:25:43.821; [   ] org.apache.solr.core.backup.BackupManager; Writing file solrconfig.xml
INFO  - 2017-11-07 22:25:43.821; [   ] org.apache.solr.core.backup.BackupManager; Writing file synonyms.txt
INFO  - 2017-11-07 22:25:43.822; [   ] org.apache.solr.core.backup.BackupManager; Writing file configoverlay.json
INFO  - 2017-11-07 22:25:43.823; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords.txt
INFO  - 2017-11-07 22:25:43.824; [   ] org.apache.solr.core.backup.BackupManager; Writing file contractions_it.txt
INFO  - 2017-11-07 22:25:43.825; [   ] org.apache.solr.core.backup.BackupManager; Writing file contractions_ca.txt
INFO  - 2017-11-07 22:25:43.825; [   ] org.apache.solr.core.backup.BackupManager; Writing file stemdict_nl.txt
INFO  - 2017-11-07 22:25:43.826; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_hy.txt
INFO  - 2017-11-07 22:25:43.827; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_no.txt
INFO  - 2017-11-07 22:25:43.828; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_id.txt
INFO  - 2017-11-07 22:25:43.828; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_da.txt
INFO  - 2017-11-07 22:25:43.829; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_ga.txt
INFO  - 2017-11-07 22:25:43.830; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_hi.txt
INFO  - 2017-11-07 22:25:43.830; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_ja.txt
INFO  - 2017-11-07 22:25:43.831; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_pt.txt
INFO  - 2017-11-07 22:25:43.832; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_hu.txt
INFO  - 2017-11-07 22:25:43.833; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_el.txt
INFO  - 2017-11-07 22:25:43.834; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_ru.txt
INFO  - 2017-11-07 22:25:43.834; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_tr.txt
INFO  - 2017-11-07 22:25:43.835; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_ar.txt
INFO  - 2017-11-07 22:25:43.836; [   ] org.apache.solr.core.backup.BackupManager; Writing file userdict_ja.txt
INFO  - 2017-11-07 22:25:43.837; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_eu.txt
INFO  - 2017-11-07 22:25:43.837; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_it.txt
INFO  - 2017-11-07 22:25:43.838; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_cz.txt
INFO  - 2017-11-07 22:25:43.839; [   ] org.apache.solr.core.backup.BackupManager; Writing file stoptags_ja.txt
INFO  - 2017-11-07 22:25:43.839; [   ] org.apache.solr.core.backup.BackupManager; Writing file contractions_fr.txt
INFO  - 2017-11-07 22:25:43.840; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_de.txt
INFO  - 2017-11-07 22:25:43.841; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_fa.txt
INFO  - 2017-11-07 22:25:43.841; [   ] org.apache.solr.core.backup.BackupManager; Writing file contractions_ga.txt
INFO  - 2017-11-07 22:25:43.842; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_ca.txt
INFO  - 2017-11-07 22:25:43.842; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_nl.txt
INFO  - 2017-11-07 22:25:43.843; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_bg.txt
INFO  - 2017-11-07 22:25:43.843; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_en.txt
INFO  - 2017-11-07 22:25:43.844; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_es.txt
INFO  - 2017-11-07 22:25:43.844; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_lv.txt
INFO  - 2017-11-07 22:25:43.845; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_ro.txt
INFO  - 2017-11-07 22:25:43.845; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_th.txt
INFO  - 2017-11-07 22:25:43.846; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_fr.txt
INFO  - 2017-11-07 22:25:43.846; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_sv.txt
INFO  - 2017-11-07 22:25:43.847; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_fi.txt
INFO  - 2017-11-07 22:25:43.848; [   ] org.apache.solr.core.backup.BackupManager; Writing file hyphenations_ga.txt
INFO  - 2017-11-07 22:25:43.848; [   ] org.apache.solr.core.backup.BackupManager; Writing file stopwords_gl.txt
INFO  - 2017-11-07 22:25:43.849; [   ] org.apache.solr.core.backup.BackupManager; Writing file params.json
INFO  - 2017-11-07 22:25:43.850; [   ] org.apache.solr.cloud.BackupCmd; Completed backing up ZK data for backupName=test