HDFS-4635. Move BlockManager#computeCapacity to LightWeightGSet. Contributed by Suresh Srinivas.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1468698 13f79535-47bb-0310-9956-ffa450edef68
Fix HADOOP-9467 attribution.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1468732 13f79535-47bb-0310-9956-ffa450edef68
HDFS-3940. Add Gset#clear method and clear the block map when namenode is shutdown. Contributed by Suresh Srinivas.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1468891 13f79535-47bb-0310-9956-ffa450edef68