ci_presubmit: init

This will be, at some point, a script to run on Gerrit presubmit (ie.
right before merge).

For now, you can manually run it to ensure that Everything At Least
Kinda Works.

Change-Id: I28b305fa81a4ca4a8e94ce4daa06fe9ae0184fe8
diff --git a/cluster/clustercfg/clustercfg.py b/cluster/clustercfg/clustercfg.py
index c3e7bd6..1396826 100644
--- a/cluster/clustercfg/clustercfg.py
+++ b/cluster/clustercfg/clustercfg.py
@@ -225,6 +225,9 @@
         return nodestrap(sys.argv[2:], nocerts=True)
     elif mode == "admincreds":
         return admincreds(sys.argv[2:])
+    elif mode == "smoketest":
+        sys.stdout.write("Smoke test passed.")
+        return 0
     else:
         usage()
         return 1