fix eslint builds within .gitlab-ci.yml

.gitlab-ci.yml

@@ -327,7 +327,7 @@ lint:javascript:
     paths:
       - node_modules/
   stage: test
-  image: "node:7.1"
+  before_script: []
   script:
     - yarn run eslint
 
@@ -337,7 +337,7 @@ lint:javascript:report:
     paths:
       - node_modules/
   stage: post-test
-  image: "node:7.1"
+  before_script: []
   script:
     - find app/ spec/ -name '*.js' -or -name '*.js.es6' -exec sed --in-place 's|/\* eslint-disable .*\*/||' {} \; # run report over all files
     - yarn run eslint-report || true # ignore exit code