svn merge -c 1536711 FIXES: MAPREDUCE-5596. Allow configuring the number of threads used to serve shuffle connections. Contributed by Sandy Ryza


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1536720 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-MAPREDUCE-4884-branch-2-gd