Revert "Deactivate failing tests for example_15"

This reverts commit 0c3c978.

Author: christophfroehlich

example_15/CMakeLists.txt

@@ -28,9 +28,8 @@ install(
 if(BUILD_TESTING)
   find_package(ament_cmake_pytest REQUIRED)
 
-  # TODO(christophfroehlich) deactivated because of bug in spawner
-  # ament_add_pytest_test(test_rrbot_namespace_launch test/test_rrbot_namespace_launch.py)
-  # ament_add_pytest_test(test_multi_controller_manager_launch test/test_multi_controller_manager_launch.py)
+  ament_add_pytest_test(test_rrbot_namespace_launch test/test_rrbot_namespace_launch.py)
+  ament_add_pytest_test(test_multi_controller_manager_launch test/test_multi_controller_manager_launch.py)
 
 endif()