cifs: do not disable noperm if multiuser mount option is not provided

Fixes small regression in implementation of new mount API.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reported-by: Hyunchul Lee <hyc.lee@gmail.com>
Tested-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Steve French <stfrench@microsoft.com>