Use correct regex to match ISO8601 date format

closes #34 (closed)

.gitlab-ci.yml

@@ -63,7 +63,7 @@ clean_up:   # This job removes older built images
     name: $TARGET_ENV
   script:
     - |
-      IMAGE_TO_BE_DELETE=($(openstack image list --sort-column Name --sort-descending -f value -c Name -c ID | grep -P " xdmod-$TARGET_ENV-\d{14}$" | sed -n $(($NUM_IMAGE_TO_KEEP+1))',$p' | awk '{print $1}'))
+      IMAGE_TO_BE_DELETE=($(openstack image list --sort-column Name --sort-descending -f value -c Name -c ID | grep -P " xdmod-$TARGET_ENV-\d{4}-\d{2}-\d{2}T\d{6}$" | sed -n $(($NUM_IMAGE_TO_KEEP+1))',$p' | awk '{print $1}'))
       echo "Images deleted:\n"
       for img in ${IMAGE_TO_BE_DELETE[@]}; do
         echo ${img}