SMB3.1.1 tree connect was only being signed when signing was mandatory
but needs to always be signed (for non-guest users).

See MS-SMB2 section 3.2.4.1.1
Signed-off-by: NSteve French <smfrench@gmail.com>
Reviewed-by: NPavel Shilovsky <pshilov@microsoft.com>
CC: Stable <stable@vger.kernel.org>