HDFS-5456. NameNode startup progress creates new steps if caller attempts to create a counter for a step that doesn't already exist. Contributed by Chris Nauroth.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1538872 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5427. Not able to read deleted files from snapshot directly under snapshottable dir after checkpoint and NN restart. Contributed by Vinay.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1538875 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HDFS-4312-trunk-gd