ci(openshift): pin router-default to control plane during E2E (#10734)

The drain_node E2E cordons one of three labelled worker nodes and drains
another, leaving the router-default Deployment's PDB unable to evict its
replicas onto the single surviving worker; the drain hangs and the test
fails intermittently on OpenShift.

Patch IngressController.spec.nodePlacement before the suite runs so
router-default lives on the control plane for the cluster's lifetime,
keeping all workers free for cordon and drain. The placement is
non-production, but the OCP cluster is destroyed at end-of-job.

Waits use observedGeneration plus rollout status, no fixed sleep.

Verified on an OCP 4.21 run of the equivalent change in the downstream
pg4k repo: the drain_node "3 pods on 2 nodes" spec (which had been
failing on the OCP nightly) is now green.

Signed-off-by: Marco Nenciarini <marco.nenciarini@enterprisedb.com>