AppSettingsView: don't block settings when DND is active

[danirabbit]

Fixes #91
Prevents blocking settings when DND is active

I know InfoBar is deprecated but we use it a lot so I think we probably will need a Granite replacement so I'm using it assuming we'll fix all infobars at once later.

[jeremypw]

This issue does not seem to affect main on elementaryos 8?

[danirabbit]

@jeremypw when you first open settings, try resizing vertically. Then open this pane and see that it forces the window height larger in main

[jeremypw]

@danirabbit Ah, OK - I see the issue now. I'll review again.

It also happens with several other plugs if you make the initial height small enough. Maybe there should be a reasonable minimum height of the main window, which all the plugs can fit in? At the moment it can be made nearly the same height as the headerbar.

[danirabbit]

I'm not sure what that value should be but I'm not opposed to adding a minimum window height 👍

[jeremypw]

I got some horrible visual glitching, when dragging the window at (fairly) small size.

[danirabbit]

@jeremypw I saw that too. I don't think there's anything I can do here about that since it seems like a GTK bug

[danirabbit]

@jeremypw looks like this also happens in Network settings

[jeremypw]

Yes, I now see it happening main and some other plugs (but not all). I guess its not a blocker for this PR then. Hope it is fixed upstream soon!

Upstream issue

[jeremypw]

Code looks good and works well.