When sleeping waiting for either local or remote advisory lock,
interrupt sleeps with the ERESTART on the suspension attempts.
Otherwise, single-threading requests are deferred until the locks are
granted for NFS files, which causes hangs.

When retrying local registration of the remotely-granted adv lock,
allow full suspension and check for suspension, for usual reasons.

Reported by: markj, pho
Reviewed by: jilles
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Approved by: re (gjb)