fix: avoid race condition by not running exec/start twice

[NekoShinobi]

When running with the lifecycle labels, this error is popping up at every interval/upgrade

time="2024-04-22T19:16:37Z" level=info msg="Command output:\nError: Exec command c37bb52a3fa2dd1489baf9f92ab17738ec0095b2f86afd9d27b75beee3bf2e31 is already running"

Looking more into it, it seems like it's related to moby/moby#42408 which I originally found through nektos/act#627 which is fixed with nektos/act#702

I took the changes and applied similarly to watchtower. I ran it locally with my initial fail test, and it seems to be clean now.

I'm not a go dev, so apologies if I have missed something.

[github-actions]

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