[simple_action_server.py] Set auto_start to false by default.

[130s]

In this QA it's explained (by @mirzashah) how bad auto_start=True could be. So I thought to turn that to False.

However because this could break existing application I don't think we should apply this change. I'm still sending this PR to ask for a confirmation.

[mikaelarguedas]

Thanks @130s for the link to the discussion.
Although the default is not optimal I agree with you that changing the default could break applications relying on the simple action server.

I'd prefer to keep the same default values in ActionServer and SimpleActionServer so I won't merge this to keep consistency and avoid breakage. I think that is why there is a warning in ActionServer rather than a different default.

It's nevertheless not great to have different defaults in the c++ and Python implementations...

We can revisit this decision in the future if we decide that consistency and recommended defaults overweight the downside of potential breakage

Thanks for pointing it out!

[130s]

Thanks for clarification @mikaelarguedas.

I've added a note on one of the tutorials I found, to raise more attention. Not sure if that's the only place to be updated though, but I hope that's enough to at least close this wontfix PR.