OAK-2172 ArrayIndexOutOfBoundsException in Segment.getRefId() protection and logs



git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/branches/1.0@1630332 13f79535-47bb-0310-9956-ffa450edef68
OAK-2115 Turn async indexer checkpoint warning log to debug
 - merged rev 1630338



git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/branches/1.0@1630339 13f79535-47bb-0310-9956-ffa450edef68