nfsd: call nfs4_put_deleg_lease outside of state_lock

Currently, we hold the state_lock when releasing the lease. That's
potentially problematic in the future if we allow for setlease methods
that can sleep. Move the nfs4_put_deleg_lease call out of the delegation
unhashing routine (which was always a bit goofy anyway), and into the
unlocked sections of the callers of unhash_delegation_locked.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>