NFSv4.1: Deal with server reboots during delegation expiration recovery

Ensure that if the server reboots while we're testing and recovering
from revoked delegations, we exit to allow the state manager to
handle matters.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Tested-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>