Don't poll for scavenges

[hayley-jean]

• Remove scavengeNotificationService from Run and logIn controllers so that the UI no longer polls for scavenge status. This prevents the 404 messages that show up in the UI if a scavenge has not been run.
  • If a 404 is received on the admin screen, stop the scavenge status poller.
  • Trigger the scavenge status poller if the scavenge button is clicked. This will allow the UI to update the scavenge status once a scavenge has been triggered.
  • If a scavenge was triggered any other way (through curl for example), the UI will need to be refreshed to see status updates.