clear_status_flags_on_sybil might want to clear more flags
clear_status_flags_on_sybil contains a comment saying "it's easy to add a new flag but forget to add it to this clause."
It looks like we may have forgot the following flags:
- bw_is_unmeasured? (set to 1?)
To deal with the root cause, should we instead zero out the entire
routerstatus_t, then copy the fields we need back in?
(This would zero new fields on sybils by default.)
We could also implement a unit test for clear_status_flags_on_sybil that checks that certain (important?) flags are cleared, or that all flags are cleared (?).