protocoldetector: Use values() instead of items()

Iterating over items is useful when we need the keys, but we don't.

Change-Id: Ide36b3ec93924ccde3a0084ad002ec980fe5c0e6
Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/34330
Reviewed-by: Dima Kuznetsov <dkuznets@redhat.com>
Reviewed-by: Piotr Kliczewski <piotr.kliczewski@gmail.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>