Fix crash encountered by the testsuite.

Running testsuite tests locally produced no errors, but when
run using the continuous integration framework, crashes occurred.

The crashes occurred due to a refcounting error that had been fixed
for a similar situation.
........

Merged revisions 420758 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@420759 65c4cc65-6c06-0410-ace0-fbb531ad65f3