HIVE-6738 : HiveServer2 secure Thrift/HTTP needs to accept doAs parameter from proxying intermediary (Dilli Arumugam via Thejas Nair)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/branch-0.13@1585198 13f79535-47bb-0310-9956-ffa450edef68