NsdService: Clear client info after resolution request is serviced.

Currently, the client requests tracked in mClientIds for resolution
requests isn't cleared at all and causes failues of additional registration
and discovery requests once the number of requests reaches MAX_LIMIT. In
addition, bubble up unhandled native events to default state of nsd state
machine.

Change-Id: Ief14e0fff644aa2698fcddd71f538820f802be58