Only a subset of users may be allowed to update the action cache
(e.g., only CI but not devs).

Today, there are 2 ways to achive the desired behavior:
  - `GetCapabilities` returning that all users are allowed to update,
    and `UpdateActionResult` returning an error that Bazel prints and
    ignores, or
  - have the users that are not allowed to update the action cache
    set `--remote_upload_local_results=false`.

Why don't we instead respect whether the remote cache supports
uploading action results?

Note that this requires support from the remote system to fully work
(i.e., it needs to return `update_enabled = false` for users that
don't have permission). Otherwise, Bazel's behavior will be the
same as before this change: failed `UpdateActionResult` do not cause
the build to fail. The only change this introduces is that Bazel
will no longer error if `--remote_upload_local_results=true`
and `GetCapabilities` returning `update_enabled = false`.

…e-respect-server-caps

This reverts commit d63c5c8.