fix(docker): pass registry-failure up

lib/datasource/docker/index.js

@@ -291,6 +291,9 @@ async function getTags(registry, repository) {
     await renovateCache.set(cacheNamespace, cacheKey, tags, cacheMinutes);
     return tags;
   } catch (err) /* istanbul ignore next */ {
+    if (err.message === 'registry-failure') {
+      throw err;
+    }
     logger.debug(
       {
         err,