Fix overlay

[jreidinger]

quoting first commit message:

Fix applying too old backup for overlays (bsc#1070726)

In general problem is that system role selection clears overlay before
creating dialog, but it does it when going back and also when going
forward. So result is that when going back it is properly cleared and
then when going forward when different extensions is chosen, it is again
cleared, but with invalid backup. So this change in the end apply backup
only when going back.

[kobliha]

I'm missing a test case

[coveralls]

Coverage increased (+0.002%) to 25.458% when pulling 5b82e89 on fix_overlay into aa6d6b3 on master.

[coveralls]

Coverage increased (+0.002%) to 25.458% when pulling 53b33c6 on fix_overlay into aa6d6b3 on master.

[mvidner]

"No description provided." please provide context for the PR.

WHY are we calling ClearOverlay a second time without an intervening SetOverlay? That is not supposed to happen.

[mvidner]

So we are at SelectSystemRole (where ClearOverlay is called) and we go Next Back Back Next, right?

[jreidinger]

@mvidner yes, see mentioned bug. In fact problematic workflow is:

1. register system
2. no extensions
3. select any role ( so first backup is stored )
4. go back to extension selection ( so first ClearOverlay is called )
5. select basesystem extension
6. select role ( here second ClearOverlay is called which removes extensions and then SetOverlay is called, but with Features that no longer have new extensions )
7. go back ( so now ClearOverlay is called with wrong backup ) and you see broken texts in roles

[coveralls]

Coverage increased (+0.004%) to 25.46% when pulling a510371 on fix_overlay into aa6d6b3 on master.

[kobliha]

Nice that we have a test for the new exception

LGTM

[mvidner]

Thanks!