It has come to my attention that GRPC uses the HTTPS_PROXY environment variables by default. This is surprising, and likely undesirable for CRDB because it turns the proxy into an availability risk and a throughput bottleneck.

I think we should probably disable the use of proxies by default for intra-node connections (but continue to use them for e.g. connecting to cloud storage in backup/restore/import). We
could add a command-line flag to re-enable them.

Whether we change the default or not, we should log at startup if a proxy is being used. This logging is worth backporting to current releases even though disabling the proxy couldn't happen until 21.1.