Don't vote HSDir if we aren't voting Valid
Similar to legacy/trac#15963 (moved) and legacy/trac#8243 (moved), if we end up taking away the Valid flag from a relay, I would like us to take away the HSDir flag too.
(I think there may still be some bug where if you take away the Valid flag, you end up taking away the Running flag soon after, accidentally. But I think that bug is different and orthogonal to this one.)
In particular, there are relays currently that are running malicious HSDirs, but I'd like the opportunity to still make use of them for other (less sensitive) positions.