MAPREDUCE-2454. plugin for generic shuffle service. (avnerb via tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1506774 13f79535-47bb-0310-9956-ffa450edef68
Merge branch 'branch-1' into HADOOP-9768-branch-1
HADOOP-9768: only allow space on Windows