Currently TaskExecutor::RemoteCommandCallbackArgs::RemoteCommandCallbackArgs contains a response that is a StatusWith<RemoteCommandResponse> where you can only get the elapsed time on success, not the error cases.

We should always return the time, even on failures.
We should also return the metadata where we have it available (as in the case of command failures)

This is needed for retries and other operations done by the callers of scheduleRemoteCommand.