A race condition existed between when Rails committed the `import_status` to
`started` and when the Sidekiq worker forked a project. If this fork was quick,
it's possible that the worker would attempt to move into the `finished` state
before the `started` state took effect.

As mentioned in https://github.com/mperham/sidekiq/wiki/Problems-and-Troubleshooting#cannot-find-modelname-with-id12345,
we should delay the worker to ensure the DB has a chance to update.

Closes #2736

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Use import_status to track async import status and give feedback to the user

Closes #2388
Closes #2400

Resolves #9285

This reverts commit 5daf44b7, reversing
changes made to 2f706fbd.

This reverts commit 957e849f, reversing
changes made to 6b9dbe9f.
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Add gitlab-shell to error message to give user a clue that something may be wrong there.

Ran into this in #2082. User was told that repositories were created when they were
not due to hooks symlink being wrong.

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Now there is a single source of information for which attribute a model
uses to be referenced, and its special character.

This would result in a 404 error in certain views.

The `save` call was being rolled back due to an error in the validation step.
Relax the validation step so that this works.

Closes #1570

This reverts commit 548f1828.