Not possible to use generic servers implementing the remote-apis as remote cache

Summary

Builstream seems to complain with the remote-apis specs (https://github.com/bazelbuild/remote-apis), but still seems to be not possible to use some of the servers that implement those apis as remote cache

What is the current bug behavior?

• It's not possible to use remote-apis servers like buildfarn and buildbarn as remote cache

What is the expected correct behavior?

• It should be possible to use servers that implement the remote-apis as remote cache