Fix ros_gz_sim.launch.py when create_own_container is enabled (backport #620)

[mergify]

🦟 Bug fix

I noticed that running the following example:

ros2 launch ros_gz_sim ros_gz_sim.launch.py world_sdf_file:=sensors_demo.sdf bridge_name:=ros_gz_bridge config_file:=/home/caguero/ros_gz_ws/src/ros_gz/ros_gz_bridge/test/config/full.yaml use_composition:=True create_own_container:=True

duplicates the number of running nodes and containers.

caguero@cold:~/ros_gz_ws$ ros2 node list
/gz_server
/gz_server
/launch_ros_1390503
/ros_gz_bridge
/ros_gz_bridge
/ros_gz_container
/ros_gz_container

After this patch:

caguero@cold:~/ros_gz_ws$ ros2 node list
/gz_server
/launch_ros_1395505
/ros_gz_bridge
/ros_gz_container

Summary

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

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This is an automatic backport of pull request #620 done by Mergify.