Merge branch 'gitlab-import-status' into 'master'

Fixed issue with GitLab import buttons having a spinner

![import](/uploads/db635f1d62affefca027d5fd4f545cd1/import.gif)

Closes #17232

See merge request !4276

app/views/import/gitlab/status.html.haml

@@ -47,7 +47,7 @@
           %td.import-target
             = repo["path_with_namespace"]
           %td.import-actions.job-status
-            = button_tag class: "btn js-add-to-import" do
+            = button_tag class: "btn btn-import js-add-to-import" do
               Import
               = icon("spinner spin", class: "loading-icon")