YARN-498. Unmanaged AM launcher does not set various constants in env for an AM, also does not handle failed AMs properly (Hitesh Shah via bikas)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1460954 13f79535-47bb-0310-9956-ffa450edef68
YARN-469. Make scheduling mode in FS pluggable. (kkambatl via tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1460961 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HDFS-4310-trunk-gd