Dir auths should consider changing their cbttestfreq param vote

Tor 0.3.1.1-alpha will reduce the default for the cbttestfreq consensus parameter from 60 to 10 (see legacy/trac#17592 (moved)).

Currently the directory authorities vote 60 for it, for robustness against a small number of dir auths choosing a harmful number.

We should consider changing our param votes to 10, to match the upcoming code.