res_timing_pthread: Fix leaky pipes.

res_timing_pthread: Fix leaky pipes.

During some refactoring the way private information for timers
was stored was changed. As a result of this the action which normally
removed the timer upon closure in res_timing_pthread was also removed
causing the timer to remain after it should using up resources.
This change ensures that the timer is removed upon closure.

ASTERISK-24768 #close
Reported by: Matthias Urlichs
patches:
 timer.patch submitted by Matthias Urlichs (license 5508)
........

Merged revisions 431807 from http://svn.asterisk.org/svn/asterisk/branches/13

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@431808 65c4cc65-6c06-0410-ace0-fbb531ad65f3