SMB3.1.1 dialect has additional security (among other) features
and should be requested when mounting to modern servers so it
can be used if the server supports it.

Add SMB3.1.1 to the default list of dialects requested.
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>