Whenever we add new extensiosn into the shared job, they are added for all branches, and there's a decent chance they don't pass in older versions, simply because they weren't tested. And then when someone tries to backport a branch, stuff is failing and that's really frustrating.

We should keep the list of extensions inside a zuul function, and split them by branch where they were added so they don't run on older branches that they weren't tested with.

{
	"REL1_25": ["FooBar"],
	"REL1_27": ["BlahBlah"]
}

And it would automatically know to add the 25 jobs to 27. Or something.