svn merge -c 1399011. FIXES: MAPREDUCE-4521. mapreduce.user.classpath.first incompatibility with 0.20/1.x (Ravi Prakash via bobby)
git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1399014 13f79535-47bb-0310-9956-ffa450edef68