introduce control variable for non alpha feature gate configuration

Some of the CSI components may need to tweak the by default enabled
feature gates for latest clusters for their operations. This
configuration knob helps them for controlling it.

Signed-off-by: Humble Chirammal <hchiramm@redhat.com>

prow.sh

@@ -349,6 +349,9 @@ configvar CSI_PROW_E2E_ALPHA "$(get_versioned_variable CSI_PROW_E2E_ALPHA "${csi
 configvar CSI_PROW_E2E_ALPHA_GATES_LATEST '' "alpha feature gates for latest Kubernetes"
 configvar CSI_PROW_E2E_ALPHA_GATES "$(get_versioned_variable CSI_PROW_E2E_ALPHA_GATES "${csi_prow_kubernetes_version_suffix}")" "alpha E2E feature gates"
 
+configvar CSI_PROW_E2E_GATES_LATEST '' "non alpha feature gates for latest Kubernetes"
+configvar CSI_PROW_E2E_GATES "$(get_versioned_variable CSI_PROW_E2E_GATES "${csi_prow_kubernetes_version_suffix}")" "non alpha E2E feature gates"
+
 # Which external-snapshotter tag to use for the snapshotter CRD and snapshot-controller deployment
 default_csi_snapshotter_version () {
 	if [ "${CSI_PROW_KUBERNETES_VERSION}" = "latest" ] || [ "${CSI_PROW_DRIVER_CANARY}" = "canary" ]; then
@@ -1254,7 +1257,8 @@ main () {
         fi
 
         if tests_need_non_alpha_cluster; then
-            start_cluster || die "starting the non-alpha cluster failed"
+	    # Need to (re)create the cluster.
+            start_cluster "${CSI_PROW_E2E_GATES}" || die "starting the non-alpha cluster failed"
 
             # Install necessary snapshot CRDs and snapshot controller
             install_snapshot_crds