smb3.1.1: allow dumping keys for multiuser mounts

When mounted multiuser it is hard to dump keys for the other sessions
which makes it hard to debug using network traces (e.g. using wireshark).

Suggested-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>