ci: Fix container entry points

* The _zola_ container image no longer contains Python, but it does
  contain `pause`.
* When using `python` as the entry point, we need to explicitly register
  a signal handler for SIGTERM, otherwise `signal.pause()` will never
  return.
* The _rsync_ container image now has a default pause entry point.

ci/podTemplate.yaml

@@ -10,11 +10,9 @@ spec:
     - python
     args:
     - -c
-    - import signal; signal.pause()
+    - |-
+      import signal
+      signal.signal(signal.SIGTERM, lambda x, y: None)
+      signal.pause()
   - name: rsync
     image: git.pyrocufflink.net/containerimages/rsync
-    command:
-    - python3
-    args:
-    - -c
-    - import signal; signal.pause()