Switch wait for port function to use wall clock time instead of counting retries and other smaller improvements

This PR includes a new major (backwards-compatible feature):

• It switches the wait for port process to use the same deadline as the warmup. This means that if the configured deadline is 90 seconds, and waiting for the service port to be up takes 30 seconds, only 60 seconds of warm-up will be done (previously this would not happen).

It also includes a bugfix when printing a warning about a failed request (would not work with post requests) and it prints error backtraces to the debug logger when something bad happens.