Fix memory leak in test_subscription_nominal (#469) (#562)
Fix memory leak in test_subscription_nominal (#469) (#562)

Narrow scope of subscription to prevent leak and separate nominal test from init/fini test.

Signed-off-by: y-okumura-isp <f87bc0fd31328561bebb104855c1d20474f2908a@isp.co.jp>
ros2/rcl,ros2/rcl