cf-trace has no way to describe an arbitrary target — it always
echoes the ip of whoever is making the http request. gather_identity
included it in the merge candidates unconditionally, so 'netcheck
--target 8.8.8.8' spliced this machine's own connecting ip onto
8.8.8.8's asn/city/org fields from the other providers, producing a
report that named an ip that was neither the target nor honestly
labeled as the local egress. exclude cf-trace from the merge whenever
an explicit target ip was requested; it's still fetched and returned
separately for the connection section's own colo/warp fields.
