fixes pgsql double free of threadstorage

A thread storage variable was being freed incorrectly, which
resulted in a double free if two queries were made in the same thread.

(closes issue #16011)
Reported by: cristiandimache
Patches:
      issue16011.diff uploaded by dvossel (license 671)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@229093 65c4cc65-6c06-0410-ace0-fbb531ad65f3