Directory authorities no longer vote in favor of the Guard flag
for relays that don't advertise directory support.
Starting in Tor 0.3.0.1-alpha, Tor clients have been avoiding using
such relays in the Guard position, leading to increasingly broken load
balancing for the 5%-or-so of Guards that don't advertise directory
support.
Fixes bug 22310; bugfix on 0.3.0.6.
