Correct bash array variable syntax

.gitlab-ci.yml

@@ -165,10 +165,10 @@ deploy_knightly:
     - |
       SERVER_TO_BE_DELETE=($(openstack server list --name ood-knightly --sort-column Image --sort-descending -f value -c ID | sed -n $(($NUM_SERVER_TO_KEEP+1))',$p'))
       IMAGE_TO_BE_DELETE=($(openstack image list --sort-column Name --sort-descending -f value -c Name | grep -P '^ood-\d{8}$' | sed -n $(($NUM_IMAGE_TO_KEEP+1))',$p'))
-      for svr in $SERVER_TO_BE_DELETE; do
+      for svr in ${SERVER_TO_BE_DELETE[@]}; do
         openstack server delete ${svr}
       done
-      for img in $IMAGE_TO_BE_DELETE; do
+      for img in ${IMAGE_TO_BE_DELETE[@]}; do
         openstack image delete ${img}
       done
   only: