Publish per-branch astara-appliance images

When built from stable branches, name astara-appliance images accordingly
and publish them as such.

This fixes a bug where master and stable branches are publishing images to the
same file on tarballs.o.o.

Change-Id: I148c35b6e0493b9a2a8b8ec0b1ced101668cb7d1

jenkins/jobs/astara.yaml

@@ -90,7 +90,13 @@
       - shell: |
           #!/bin/bash -xe
           tox -e build_image
-          mv build/astara_appliance*.qcow2 $WORKSPACE/
+          if [[ "$ZUUL_REFNAME" =~ "stable" ]]; then
+              branch="$(echo $ZUUL_REFNAME | cut -d/ -f2)"
+              branch_tag="_$branch"
+          else
+              branch_tag=""
+          fi
+          mv build/astara_appliance*.qcow2 $WORKSPACE/astara_appliance$branch_tag.qcow2
 
     publishers:
       - scp: