cifs: check MaxPathNameComponentLength != 0 before using it

commit f74bc7c6 upstream.

And fix tcon leak in error path.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: David Disseldorp <ddiss@samba.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>