hydra-notify: print out log lines indicating it is or is not launching the exporter

Dependencies

• [2] 4H6FVIWG hydra-notify: make the prometheus endpoint configurable, default-off
• [*] IE2PRAQU hydra-queue-runner: Send build notifications

Change contents

• edit in src/script/hydra-notify at line 70
  [2.1458]

  [2.1458]
  + print STDERR "Starting the Prometheus exporter, listening on http://${\$promCfg->{'listen_address'}}:${\$promCfg->{'port'}}/metrics.\n";
• edit in src/script/hydra-notify at line 81
  [2.1786]

  [2.1786]
  + } else {

  + print STDERR "Not starting the hydra-notify Prometheus exporter.\n";