[master] Optimize number of RPC calls to HBase in table input format

Author: mahmoudeariby

Summary: Added ConcurrentSkipListMap to be able to cache number of regions for a specific table,job so we don't do more RPC calls when need this number again.

Test Plan:
do those calls
initTableReducerJob()
setNumReduceTasks()
limitNumReduceTasks()
check how many times we had to do HTable.getRegionsInfo()

Reviewers: manukranthk

Reviewed By: manukranthk

CC: liyintang

Differential Revision: https://phabricator.fb.com/D902790

Task ID: 1753210

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1513999 13f79535-47bb-0310-9956-ffa450edef68