Cleanup reference leaks in res_jabber

Cleanup reference leaks in res_jabber

res_jabber.c had a number of places where astobjs would be referenced and have their
reference counts bumped without having a dereference made before the object lost scope.
This patch adds a number of ASTOBJ_UNREFs to resolve that.

Review: https://reviewboard.asterisk.org/r/1478/
........

Merged revisions 342545 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@342546 65c4cc65-6c06-0410-ace0-fbb531ad65f3