[cmd/opampsupervisor] ensure OnConnectClosed is hooked up

OnConnectionClose was never hooked up to the server's OnConnectionClose, causing the restart of the agent to never be able to reconnect.

Signed-off-by: Alex Boten <[email protected]>

cmd/opampsupervisor/supervisor/server.go

@@ -44,7 +44,8 @@ func (fs flattenedSettings) OnConnecting(request *http.Request) serverTypes.Conn
 	return serverTypes.ConnectionResponse{
 		Accept: true,
 		ConnectionCallbacks: serverTypes.ConnectionCallbacks{
-			OnMessage: fs.OnMessage,
+			OnMessage:         fs.OnMessage,
+			OnConnectionClose: fs.OnConnectionClose,
 		},
 	}
 }