Reduce duplication in import views

The following discussion from !8370 (merged) should be addressed:

• @zj started a discussion:

  Should an issue be opened on the duplication between these status pages between importers? Is there one?

The following views all share the same common logic that right now feels quite a bit duplicated:

• app/views/import/bitbucket/status.html.haml
• app/views/import/bitbucket_server/status.html.haml
• app/views/import/fogbugz/status.html.haml
• app/views/import/gitlab/status.html.haml
• app/views/import/google_code/status.html.haml