testcases/containers: variable not used/assigned

flake8 complains that global container_tests is unused and it
is never assigned in scope.

Fixed the same by removing the unused global declaration within
the function and adding an appropriate comment.

Signed-off-by: Shwetha K Acharya <[email protected]>

Author: Shwetha-Acharya

testcases/containers/test_containers.py

@@ -24,7 +24,7 @@
 
 
 def load_container_tests() -> int:
-    global container_tests
+    # This modifies the global container_tests
     with open(container_tests_file) as f:
         ct = yaml.safe_load(f)
     if ct is None: