usrloc: safety check for debug message printing path value from rpc add command

- reported and patch by Thomas Arimont, FS#467
git failed to do fast forward and rebase to avoid the merge notification

Merge branch 'master' of ssh://git.sip-router.org/kamailio

* 'master' of ssh://git.sip-router.org/kamailio:
  Rollback accidental changes from commit (74f53b7d7f6ff00144152aff453e6b388447320c)
  pkg/kamailio/deb: update to 4.2.0~pre0