Page is not reloaded periodically to check if rebase is finished

• Zendesk ticket: https://gitlab.zendesk.com/agent/tickets/10040
• Dev link: None
• GitLab version: 8.1

Expected behavior

When a user rebases a merge request the page should periodically reload to check the rebase status. If the rebase is done the 'accept' button should appear.

Observed behavior

The page reloads once and says the rebase is in progress. The page is not subsequently reloaded to check again. User must manually reload and then sees 'accept' button if rebase is finished.

Next steps

@vsizov Can you take a look, please?