.prow.sh: work around for installing RBAC files

There are multiple reasons why installing the external-health-monitor-controller
cannot use the "normal" code:
- the RBAC file is not where https://github.com/kubernetes-csi/csi-release-tools/blob/7fe51491d8f56d0d459bf9abb9692bc9f96d2b75/prow.sh#L1243-L1258
  expects it
- the variable for overriding the RBAC source in https://github.com/kubernetes-csi/csi-driver-host-path/blob/9be5dd74a7fc2436c4334820156056b74821998e/deploy/util/deploy-hostpath.sh#L157-L158
  does not match the command name (csi-external-health-monitor-controller -> CSI_EXTERNAL_HEALTH_MONITOR_CONTROLLER_RBAC !=
  CSI_EXTERNALHEALTH_MONITOR_RBAC_YAML)

This solution was chosen because it can be done locally. Renaming the RBAC
variable in csi-driver-host-path and moving files would have affected multiple
repos and might not have been possible without some collateral damage.

.prow.sh

@@ -2,4 +2,29 @@
 
 . release-tools/prow.sh
 
+# There are multiple reasons why installing the external-health-monitor-controller
+# cannot use the "normal" code:
+# - the RBAC file is not where https://github.com/kubernetes-csi/csi-release-tools/blob/7fe51491d8f56d0d459bf9abb9692bc9f96d2b75/prow.sh#L1243-L1258
+#   expects it
+# - the variable for overriding the RBAC source in https://github.com/kubernetes-csi/csi-driver-host-path/blob/9be5dd74a7fc2436c4334820156056b74821998e/deploy/util/deploy-hostpath.sh#L157-L158
+#   does not match the command name (csi-external-health-monitor-controller -> CSI_EXTERNAL_HEALTH_MONITOR_CONTROLLER_RBAC !=
+#   CSI_EXTERNALHEALTH_MONITOR_RBAC_YAML)
+#
+# The following hack works around that mismatch. It was added because it could be rolled
+# out without updating csi-release-tools and csi-driver-host-path.
+CSI_PROW_DRIVER_INSTALL_ORIGINAL="${CSI_PROW_DRIVER_INSTALL}"
+CSI_PROW_DRIVER_INSTALL=install_csi_driver_health_monitor
+install_csi_driver_health_monitor () (
+    set -x
+    images="$1"
+
+    if ${CSI_PROW_BUILD_JOB}; then
+       # Add the RBAC env variable. The prow.sh code did not find the file.
+        images+=" CSI_EXTERNALHEALTH_MONITOR_RBAC=$(pwd)/deploy/kubernetes/external-health-monitor-controller/rbac.yaml"
+    fi
+
+    "${CSI_PROW_DRIVER_INSTALL_ORIGINAL}" "$images"
+    set +x
+)
+
 main