Check for an act on failures to update contacts during registration.

There was an underlying issue in a realtime backend where database updates
would fail. Since we were not checking for failure, we would end up in a
strange state where the old database entry was still present but Asterisk
thought that it had been updated. Now when an entry fails to update, we
print a warning and delete the old contact from sorcery so there is no
mismatch between foreground and backend state.

Patches:
	res_pjsip_registrar.patch by John Hardin (License #6512)



git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@413358 f38db490-d61c-443f-a65b-d21fe96a405b