the `[sig-imageregistry][Feature:ImageStreamImport][Serial][Disruptive] ImageStream API` tests (all of them) modify the image.config.openshift.io. This ripples to the MCO and the openshfit-apiserver (at least). This causes every machine to restart at the same time that the openshift-apiserver rolls out. It then changes the configuration back.
However, the test doesn't wait for a stable system coming back. this results in an unstable cluster for the tests that follow.
[Disruptive] keyword has been added, and removed from the test suite https://prow.ci.openshift.org/view/gs/origin-ci-test/logs/release-openshift-origin-installer-e2e-aws-serial-4.6/1304146128584839168