PIG-3861: duplicate jars get added to distributed cache (chitnis via rohini)

git-svn-id: https://svn.apache.org/repos/asf/pig/branches/branch-0.14@1633944 13f79535-47bb-0310-9956-ffa450edef68
PIG-3456: Reduce threadlocal conf access in backend for each record (rohini)

git-svn-id: https://svn.apache.org/repos/asf/pig/branches/branch-0.14@1633956 13f79535-47bb-0310-9956-ffa450edef68