res_pjsip_config_wizard: Cleanup load unload

While investigating other unload issues I realized that the load/unload process 
for the config wizard was pretty ugly so I've refactored it as follows...

When the res_pjsip sorcery instance is created the config_wizard bumps it's own 
module reference to prevent it from unloading while the sorcery instance is 
still active.  When res_pjsip unloads and it's sorcery instance is destroyed, 
the config wizard unrefs itself which then allows itself to unload cleanly.  
Since the config wizard now can't load after res_pjsip or unload before it 
(which should have been the correct behavior all along), I was able to remove 
the chunks of code in both load_module and unload_module that handled that case.

Ran the testsuite tests to insure there were no functional changes and REF_DEBUG 
to insure that Asterisk was shutting down cleanly with no FRACKs or leaks.

Tested-by: George Joseph
Review: https://reviewboard.asterisk.org/r/4610/
........

Merged revisions 434619 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@434620 65c4cc65-6c06-0410-ace0-fbb531ad65f3