In the AWS API (generally) we tag things we create, and then we filter
to find them. However, creation & tagging are typically two separate
calls. So there is a chance that we will create an object, but fail to
tag it.
We fix this (done here in the case of security groups, but we can do
this more generally) by retrieving the resource without a tag filter.
If the retrieved resource has the correct tags, great. If it has the
tags for another cluster, that's a problem, and we raise an error. If
it has no tags at all, we add the tags.
This only works where the resource is uniquely named (or we can
otherwise retrieve it uniquely). For security groups, the SG name comes
from the service UUID, so that's unique.
Fixes#11324
22d719018a