Merge Widget Bug when using Fast-Forward merge strategy with approvals

When using Fast-Forward merge strategy with approvals, there is a bug in the merge widget. There seem to be several issues here so I'll list them out. If we need to split into multiple issues we can, but they may be small bugs all related to each other.

1. When the page first loads, the Rebase button is active even though the approval status hasn't been checked.
2. Once the approvals finish checking, assuming the MR has necessary approvals, the Rebase button becomes deactivated after about 5 seconds and says "Rebasing is disabled until merge request has been approved.", which isn't correct.

See the GIF below for the example on GitLab.com. Note that you'll have to wait for the 5 second pause between when the approvals show up and the Rebase button deactivates.