title: Teamcity agent in disconnected state (Agent has unregistered (will upgrade))
body: <p>Teamcity build agent in disconnected state (Agent has unregistered (will upgrade)) on the server UI.
  The build agent service was in hung state tried reboot but still didn't work so manually upgraded the TC build agent with the version server had. Rebooted the build agent service. Still disconnected. Please suggest.</p>