When an app is uninstalled the app row on the installed apps page does an
unreveal animation. The signal to detect the completion of this animation
is connected after it is initiated. If the animation occurs immediately
(e.g. the page is not visible) then the signal is missed. When the app is
reinstalled the row is there but not visible and G-S does nothing.

To reproduce:
1. Open GNOME Software
2. Go to installed tab
3. Click on an installed app
4. Remove this app
5. Install this app
6. Click back button to return to Installed page.

Expected result:
App is shown in the Installed page.

Observed result:
App is not shown in the Installed page.

Solved by connecting the signal handler before the unreveal.

A low risk bug could remain that a user installs the app again before the
unreveal animation completes, thus the row is removed even though the
apps is installed. This seems unlikely due to apps taking time to install.