HBASE-9709: LogReplay throws NPE when no KVs to be replayed in a WALEdit

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1529247 13f79535-47bb-0310-9956-ffa450edef68
Merge branch 'trunk' of github.com:apache/hbase into clean
Merge branch 'clean' into 9612_v13