Fix make recipe mapping in test runner (#6561)

.github/workflows/packaging-test-pipelines.yml

@@ -3,6 +3,8 @@ name: Build tests in packaging images
 on:
   push:
     branches: "**"
+  pull_request:
+    types: [opened, reopened,synchronize]
 
   workflow_dispatch:
 

src/test/regress/citus_tests/run_test.py

@@ -98,7 +98,7 @@ with open(tmp_schedule_path, "a") as myfile:
 # find suitable make recipe
 if "isolation" in test_schedule:
     make_recipe = 'check-isolation-custom-schedule'
-if "failure" in test_schedule:
+elif "failure" in test_schedule:
     make_recipe = 'check-failure-custom-schedule'
 else:
     make_recipe = 'check-custom-schedule'