BUG-1070: allow for URL registration failing

As part of the error reporting effor, the API contract will change, such
that the URLs can get parsed during registration, potentially throwing a
checked exception. This adds the preparatory groundwork and optimized
the codepath, as it's called repeatedly during controller startup.

Change-Id: I7c5d97c7be6cc488f8b61a99d8e27804ce24e523
Signed-off-by: Robert Varga <rovarga@cisco.com>