supervisor: Include STARTING processes in 'only_running' processes.

Because `STARTING` processes are on their way up, they should
effectively be counted as `RUNNING`, since the passage of time will
make them so.

scripts/lib/supervisor.py

@@ -56,6 +56,7 @@ def list_supervisor_processes(
 
         if only_running is None:
             results.append(name)
-        elif only_running == (process["statename"] == "RUNNING"):
+        elif only_running == (process["statename"] in ("RUNNING", "STARTING")):
             results.append(name)
+
     return results