Don't vote HSDir if we aren't voting Fast

Right now when you spin up a new relay, it gets the HSDir flag before it gets measured. So for the sybil attackers that are aiming to mess with hidden service descriptors in some way, we have to notice them faster than we have to notice other sybils. This is no fun, and easy to fix with very few downsides.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information