Add gating

This won't do anything in rawhide, but once it is moved to release
branches, it will catch really broken builds.

gating.yaml

@@ -0,0 +1,7 @@
+--- !Policy
+product_versions:
+  - fedora-*
+decision_context: bodhi_update_push_testing
+rules:
+  - !PassingTestCaseRule {test_case_name: dist.depcheck}
+  - !PassingTestCaseRule {test_case_name: working}