cifs: always revalidate hardlinked inodes when using noserverino

The old cifs_revalidate logic always revalidated hardlinked inodes.
This hack allowed CIFS to pass some connectathon tests when server inode
numbers aren't used (basic test7, in particular).

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>