Give sorcery instances a reference to their wizards.

On graceful shutdown, sorcery wizards are all killed off, but it is
possible for sorcery instances to still have dangling pointers after
this, possibly causing a crash. Giving the sorcery instances a reference
to their wizards ensures that the wizard reference will remain valid for
the lifetime of the sorcery instance.

Review: https://reviewboard.asterisk.org/r/3401
........

Merged revisions 411295 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@411296 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/sorcery.c

@@ -680,6 +680,8 @@ static void sorcery_object_wizard_destructor(void *obj)
 	if (object_wizard->wizard) {
 		ast_module_unref(object_wizard->wizard->module);
 	}
+
+	ao2_cleanup(object_wizard->wizard);
 }
 
 /*! \brief Internal function which creates an object type and adds a wizard mapping */
@@ -707,7 +709,7 @@ static int sorcery_apply_wizard_mapping(struct ast_sorcery *sorcery, const char
 
 	ast_module_ref(wizard->module);
 
-	object_wizard->wizard = wizard;
+	object_wizard->wizard = ao2_bump(wizard);
 	object_wizard->caching = caching;
 
 	ao2_link(object_type->wizards, object_wizard);