This check was originally added in 962765a3, with the intent of
preventing relays with 0 measured bandwidth from being listed in the
consensus (part of fixing #13000).
Currently, that decision and other relevant places effectively use
`dirserv_get_credible_bandwidth_kb`, which prefers bwauth-measured
bandwidth over the self-reported `bandwidthcapacity`, making this check
mostly redundant.
i.e. this change should only affect behavior when the relay has uploaded
a descriptor with `bandwidthcapacity=0` *and* we have a non-zero
measured bandwidth, in which case we'll still trust the measured
bandwidth. This is what we want when bootstrapping a network (e.g. for
testing), since it allows us to initialize bandwidths using a bandwidth
authority file.
A relay can still cause `router_is_active` to return false by setting
the hibernate flag.
Also see discussion in #40917.
Fixes#40917.
4fc43ebdee