Bugzilla

### Beta/Release Uplift Approval Request
* **User impact if declined**: Clients can get into a state where the UI shows Applying instead of Restart when update staging fails due to the maintenance service being disabled.
* **Is this code covered by automated tests?**: Yes
* **Has the fix been verified in Nightly?**: Yes
* **Needs manual test from QE?**: Yes
* **If yes, steps to reproduce**: From comment #0

Preconditions
    Install an older version of Firefox ex (Firefox 68.0b1 (20190513111358) or Firefox 68.0a1 (20190511220902)).
    Disable Mozilla Maintenance Service.

Steps to reproduce

    Launch Firefox and open browser console.
    Wait for the update download to complete and wait for about 10 seconds after completion.
    Click the about Firefox button from the Hamburger > Help menu.
* **List of other uplifts needed**: None
* **Risk to taking this patch**: Low
* **Why is the change risky/not risky? (and alternatives if risky)**: There were 2 instances where the updater set the update to pending when there was an error so it would be instead applied on restart. This patch sets those two cases to an error and it changes UpdateService.jsm to handle these two errors like it already does for other errors.
* **String changes made/needed**: None

### Beta/Release Uplift Approval Request
* **User impact if declined**: Clients can get into a state where the UI shows Applying instead of Restart when update staging fails due to the maintenance service being disabled.
* **Is this code covered by automated tests?**: Yes
* **Has the fix been verified in Nightly?**: Yes
* **Needs manual test from QE?**: Yes
* **If yes, steps to reproduce**: From comment #0

Preconditions

    Install an older version of Firefox ex (Firefox 68.0b1 (20190513111358) or Firefox 68.0a1 (20190511220902)).
    Disable Mozilla Maintenance Service.

Steps to reproduce

    Launch Firefox and open browser console.
    Wait for the update download to complete and wait for about 10 seconds after completion.
    Click the about Firefox button from the Hamburger > Help menu.
* **List of other uplifts needed**: None
* **Risk to taking this patch**: Low
* **Why is the change risky/not risky? (and alternatives if risky)**: There were 2 instances where the updater set the update to pending when there was an error so it would be instead applied on restart. This patch sets those two cases to an error and it changes UpdateService.jsm to handle these two errors like it already does for other errors.
* **String changes made/needed**: None