Reduce number of docker pulls on ci

[silverwind]

Should reduce errors like https://drone.gitea.io/go-gitea/gitea/32989/7/2 by only pulling each distinct image once per pipeline. Also remove useless pull: default entries.

[techknowlogick]

On ARM64 it is ok if we do pull always as we are paying for a pro dockerhub account, and have credentials passed, however as amd64 is auto scaled I haven’t setup credentials for those as they usually only last up to 1 hour.

[silverwind]

it is ok if we do pull always

I guess it's still pointless to pull the same image twice in a pipeline, even if we have no limit.

[zeripath]

I think our integration tests take so long that anything that makes them take a shorter time has to be good.

[techknowlogick]

But we aren't truly pulling each time, rather it does a docker pull and checks if there is a new image and if not carries on as per usual. This is useful for us as we tag for ex. Golang:1.15 which "auto updates" on every minor version change so we don't need many maintenance updates to increase minor version

[silverwind]

The only downside here is that one needs to carfully check where a image first occured in a pipeline, so it's a bit more work than just using pull:always everywhere.

[silverwind]

@techknowlogick that should still be happening. All this PR does is eliminate subsequent pulls of the same image in the same pipeline.

[techknowlogick]

Ah I missed that. Thanks for clarifying:)

[techknowlogick]

🚀