OAK-2192 Concurrent commit during compaction results in mixed segments
 - adapted compaction test from OAK-2045

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1645888 13f79535-47bb-0310-9956-ffa450edef68
OAK-2192 Concurrent commit during compaction results in mixed segments
 - loosened compaction test a bit

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1645901 13f79535-47bb-0310-9956-ffa450edef68