[CIFS] Allow cifsd to suspend if connection is lost

Make cifsd allow us to suspend if it has lost the connection with a server

Ref: http://bugzilla.kernel.org/show_bug.cgi?id=6811



Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Steve French <sfrench@us.ibm.com>
(cherry picked from 27bd6cd87b0ada66515ad49bc346d77d1e9d3e05 commit)