HDFS-2882. DN continues to start up, even if block pool fails to initialize (Contributed by Vinayakumar B)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1590941 13f79535-47bb-0310-9956-ffa450edef68
fix for hdfs05168. addressing comments on the JIRA.
minor fixes
Merge branch 'trunk' into HDFS-5168-2