bootkube.sh: pivot bootstrap node for OKD installs

OKD is using plain FCOS, which doesn't have MCD binary to pivot.
It should extract it from machine-config-daemon image and run pivot manually.
This also extract necessary files and manifests from machine-os-content image

data/data/bootstrap/files/usr/local/bin/release-image-download.sh.template

@@ -17,3 +17,20 @@ do
     echo "Pull failed. Retrying $RELEASE_IMAGE..."
 done
 
+{{if .IsOKD -}}
+# Pivot bootstrap to FCOS + OKD machine-os-content
+if [ ! -f /opt/openshift/.pivot-done ]; then
+  . /usr/local/bin/release-image.sh
+
+  # Run pre-pivot.sh script to update bootstrap node
+  MACHINE_CONFIG_OSCONTENT=$(image_for machine-os-content)
+  while ! podman pull --quiet "$MACHINE_CONFIG_OSCONTENT"
+  do
+      echo "Pull failed. Retrying $MACHINE_CONFIG_OSCONTENT..."
+  done
+  mnt=$(podman image mount "${MACHINE_CONFIG_OSCONTENT}")
+  pushd ${mnt}/bootstrap
+    . ./pre-pivot.sh
+  popd
+fi
+{{end -}}

pkg/asset/ignition/bootstrap/bootstrap.go

@@ -59,6 +59,7 @@ type bootstrapTemplateData struct {
 	Registries            []sysregistriesv2.Registry
 	BootImage             string
 	PlatformData          platformTemplateData
+	IsOKD                 bool
 }
 
 // platformTemplateData is the data to use to replace values in bootstrap
@@ -278,6 +279,7 @@ func (a *Bootstrap) getTemplateData(installConfig *types.InstallConfig, releaseI
 		BootImage:             string(*rhcosImage),
 		PlatformData:          platformData,
 		ClusterProfile:        clusterProfile,
+		IsOKD:                 installConfig.IsOKD(),
 	}, nil
 }