kola: ignition config sizes for tests can become too large to pass to instances

[saqibali-2k]

Previously, non-exclusive-test config sizes had grown to a point where aws
userdata limit was exceeded (as seen in #1030). Compressing the config
has solved the problem for now, but we will likely see down the road. Let's try to come
up with a more robust solution.

[saqibali-2k]

One approach that was discussed in #1030 (comment):

For the long term solution, I was thinking that we could just go with jlebon's earlier
suggestion of adapting coreos/coreos-assembler#2516 to further constrain buckets
depending on config size. For any test that is exclusive and has a config size that is too large, we
could add a remote config the way it was done in this PR: coreos/fedora-coreos-config#1232.

[dustymabe]

This should be fixed by coreos/coreos-assembler@ce03266 (part of coreos/coreos-assembler#2516)