SOLR-6776: only clear changesSinceCommit on a hard commit so tlog will still be flushed on a softCommit

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1642946 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6653: should return error code >0 when something fails

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1642952 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6756: A first pass at making the cloud-dev scripts work again.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1642963 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-6089: Tune CompressionMode.HIGH_COMPRESSION

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1642981 13f79535-47bb-0310-9956-ffa450edef68