Update tests to use new pid code

 - Check for the existance of @config_env['pid_dir'] before trying to
   use it.
 - Specify pid_dir and log_dir in test config to avoid them defaulting
   to a location requiring root permissions during tests.
 - Update names of the flapjack*receiver commands so that the pidfiles
   match the defaults.
 - Update daemon test code to use new pidfile locations.
 - Add mandatory error messages to exit_now! statements