Trying to detect systemd service

If the systemd service didn't launch us, then simply loop
forever with a 15 minute sleep in between each loop. This will
make it easier to integrate into Docker, which I'm trying to
make a supported configuration.

I still think running via systemd unit & timer is a better
method, and docker images might actually have systemd inside
depending on the image base? If so, then we'll simply put
a pre-made systemd service and timer unit in the Dockerfile and
then automatically install them upon launch.

discorss.py

@@ -210,4 +210,12 @@ def main():
 
 
 if __name__ == "__main__":
+    if os.environ["INVOCATION_ID"]:
         main()
+    else:
+        try:
+            while True:
+                main()
+                time.sleep(15 * 60)
+        except KeyboardInterrupt:
+            exit(0)