cifs: Delete a stray unlock in cifs_swn_reconnect()

The unlock is done in the caller, this is a stray which leads to a
double unlock bug.

Fixes: bf80e5d4 ("cifs: Send witness register and unregister commands to userspace daemon")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Samuel Cabrero <scabrero@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>