htraced: improvements to logging, daemon startup, and configuration
- htraced should log a startup message as the first thing it does, so that it can be obvious when a new htraced instance is starting.
- Configuration keys that begin with htraced. should be honored only by htraced, not by the htrace tool or any other code. This will allow us to configure the log file path separately for htraced versus the command-line tool.
- htraced should attempt to open the configured HTTP port as the first thing it does. This way, if there is another htraced instance running, we bail out early rather than potentially messing up the current running instance.