SMB3: Allow SMB3 FSCTL queries to be sent to server from tools

For debugging purposes we often have to be able to query
additional information only available via SMB3 FSCTL
from the server from user space tools (e.g. like
cifs-utils's smbinfo).  See MS-FSCC and MS-SMB2 protocol
specifications for more details.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>