🍒dbusactivationrunner: only activate well-formed services

From the specification:

The application must name its desktop file in accordance with the naming recommendations in the introduction section (e.g. the filename must be like org.example.FooViewer.desktop).

When an application is in violation of this we'll not dbus activate it lest libdbus assert crashes in our face

BUG: 475266 (cherry picked from commit 246ea181)