SMB3: Honor 'seal' flag for multiuser mounts

commit cc15461c73d7d044d56c47e869a215e49bd429c8 upstream.

Ensure multiuser SMB3 mounts use encryption for all users' tcons if the
mount options are configured to require encryption. Without this, only
the primary tcon and IPC tcons are guaranteed to be encrypted. Per-user
tcons would only be encrypted if the server was configured to require
encryption.

Signed-off-by: Paul Aurich <paul@darkrain42.org>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>