GCP Serial Failing on Simultaneous MachineSet Scaling Test

test=[sig-cluster-lifecycle][Feature:Machines][Serial] Managed cluster should grow and decrease when scaling different machineSets simultaneously [Timeout:30m][apigroup:machine.openshift.io] [Suite:openshift/conformance/serial]

Appears to be perma-failing on gcp serial jobs.

We're at the edge of our visible data, but it looks like this may have happened around July 7

Sample failure: https://prow.ci.openshift.org/view/gs/origin-ci-test/logs/periodic-ci-openshift-release-master-ci-4.14-e2e-gcp-sdn-techpreview-serial/1681814026218115072