Use different way to get old instance id

Since we don't delete old instance,
using instance name will result in getting multiple ids

.gitlab-ci.yml

@@ -70,7 +70,12 @@ test:
   tags:
     - build
   script:
-    - export OLD_INSTANCE_ID=$(openstack server list --name ood-knightly -c ID -f value)
+    - OLD_INSTANCE_IP=$(openstack floating ip list --floating-ip-address $CHEAHA_IP -c "Fixed IP Address" -f value)
+    - echo $OLD_INSTANCE_IP
+    - |
+      if [ ! -z $OLD_INSTANCE_IP ]; then
+        export OLD_INSTANCE_ID=$(openstack server list --name ood-knightly --ip $OLD_INSTANCE_IP -c ID -f value)
+      fi
     - echo OLD_INSTANCE_ID=$OLD_INSTANCE_ID | tee -a instance.env
     - |
       cat > user_data.txt << OEOF