[CIFS] Do not send newer QFSInfo to legacy servers which can not support it

Fix dialect negotiation to save off when we have negotiated lanman.
This allows us to avoid sending some somewhat newer requests that the server
can not handle and go directly to the older version (infolevel) of the same
call. Make sure we try to negotiate a level which allows us to get the
server OS (which we check so we can detect Win9x vs. other legacy servers
and eventually work around the Win9x DOS time bug (they reverse date/time
fields).

Signed-off-by: Steve French <sfrench@us.ibm.com>