Fix reloading of peer when a user is requested.

Fix reloading of peer when a user is requested.

Prevent peer reloading from causing multiple MWI subscriptions to be created when using realtime.  This had the effect of sending one NOTIFY for every time a sip peer made a call, in one case eventually overwhelming  the phone and causing it to reboot.

(closes issue #18342)
Reported by: nivek
Patches:
      issue0018342p1.patch uploaded by nivek (license 636)
Tested by: nivek

Review: https://reviewboard.asterisk.org/r/1029/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@296352 65c4cc65-6c06-0410-ace0-fbb531ad65f3