smb3: do not setup the fscache_super_cookie until fsinfo initialized

We were calling cifs_fscache_get_super_cookie after tcon but before
we queried the info (QFS_Info) we need to initialize the cookie
properly.  Also includes an additional check suggested by Paulo
to make sure we don't initialize super cookie twice.

Suggested-by: David Howells <dhowells@redhat.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>