res_pjsip_config_wizard.c: Refactor load process

res_pjsip_config_wizard.c: Refactor load process

The way we have been initializing the config wizard prevented it
from registering its objects if res_pjsip happened to load
before it.

* We now use the object_type_registered sorcery observer to kick
things off instead of the wizard_mapped observer.

* The load_module function now checks if res_pjsip has been loaded
already and if it was it fires the proper observers so the objects
load correctly.

Resolves: #816

UserNote: The res_pjsip_config_wizard.so module can now be reloaded.
(cherry picked from commit 5c437c572479b0e62126c56858002fb2216aa40c)