Decide/implement whether to accept both answers from bridgestrap and bridge scanner or only the bridge scanner

Once #143 (closed) is implemented, which might not require any changes since the bridge scanner is implementing the same API (tpo/network-health/onbasca#136 (closed)), we should figure out whether bridgestrap will be just replaced by the bridge scanner or rdsys should be asking about bridges to both and how to interpret/merge their responses.