HIVE-8705: Support using pre-authenticated subject in kerberized HiveServer2 HTTP mode (Vaibhav Gumashta reviewed by Thejas Nair)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/branch-0.14@1636794 13f79535-47bb-0310-9956-ffa450edef68