Fix parallel invocation of stack --docker (#3400)

[SimSaladin]

• Any changes that could be relevant to users have been recorded in the ChangeLog.md
• The documentation has been updated, if necessary.

See issue #3400 for background.

Thanks to @mgsloan for your help on how to go about this! Turned out the fix was actually quite trivial.

A patched stack is already live in our CI. I will report findings here later.

[decentral1se]

A patched stack is already live in our CI. I will report findings here later.

🍰

[mgsloan]

That looks great, thanks! Curious to here if it works well, but this looks like the right thing to me so merging.

I also opened #3407 . Not an issue with this in particular, just the use of lockfiles in general.

[SimSaladin]

As expected, the pipelines run that much more smoother now, no issues since!