Previously we tolerated up to 1.5 connections for every relay we were connected to, and didn't warn if we had fewer than 5 connections total.
Now we tolerate up to 1.5 connections per relay, and up to 4 connections per authority, and we don't warn at all when we have fewer than 25 connections total.
Fixes bug 33880, which seems to have been provoked by our #17592 (closed) change in 0.3.5.