NLM: Fix a memory leak in nlmsvc_testlock

The recent fix for a circular lock dependency unfortunately introduced a
potential memory leak in the event where the call to nlmsvc_lookup_host
fails for some reason.

Thanks to Roel Kluin for spotting this.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>