testmap: Declare empty cockpituous tests

This is going to be useful to write an integration test for
cross-project testing in cockpituous' `run-local.sh`. That at least
needs figuring out the default branch, which requires an entry in the
test map.

lib/testmap.py

@@ -34,6 +34,10 @@ def contexts(image, *scenarios: Iterable[str], repo: Optional[str] = None):
         # currently no tests outside of GitHub actions, but declares primary branch
         'main': [],
     },
+    'cockpit-project/cockpituous': {
+        # no real tests on our infra, but used in cockpituous' own integration tests
+        'main': [],
+    },
     'cockpit-project/cockpit': {
         'main': [
             *contexts('arch', COCKPIT_SCENARIOS),