CASMINST-7394 Add workflowRef label unique to image to avoid overwriting

We use workflowRef label to identify workflow, which needs to be re-triggered
to update image with latest CVE fixes. We also try to re-trigger base image,
but workflowRef label of base image is susually overwritten by descendant image build.
To avoid that, we will add workflowRef.<image> label, which is unique to
image name.

Author: mtupitsyn

build-sign-scan/action.yaml

@@ -171,6 +171,7 @@ runs:
           org.opencontainers.image.vendor=Hewlett Packard Enterprise Development LP
           buildDate=${{ steps.strings.outputs.now }}
           workflowRef=${{ github.workflow_ref }}
+          workflowRef.${{ inputs.docker_repo }}:${{ inputs.docker_tag }}=${{ github.workflow_ref }}
 
     - name: Build Image
       id: build