HBASE-9423 Log splitting should not start till HDFS out of safe mode

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1519910 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-YAHOO-666-trunk-gd