Improve error handling in listener services.

Check explicitly for null listeners in NMS, throwing
IllegalArgumentException (on the small list of exceptions
that survive RPC boundaries) with a message.

Normally this situation is caused by listeners that attempt to
perform NM-related actions before they are bound.  Check for
this case in the base NLS class and avoid the call to NM if we
know it will fail.

Although it's tempting to throw an IllegalStateException on the
client side, preserve the existing semantics for backwards-compatibility
purposes.  That is, silently fail (or return null) - and provide a
log warning.

Bug:12805707
Change-Id: I0d92fd0d460a8592e8a23fd8fd718ae2ba3bd4c7