Don't allow updates with an active search
When the search entry has some text to filter DBus names, any change in the list of DBus names refreshes the list, and also unselects and clears any selection made by the user. This means that if the user entered some letters to find an specific DBus service, and then (s)he is inspecting the objects and interfaces, suddendly the selection will disappear and the user will have to select again the service, expand the object and the interface... and this will happen over and over again every couple of seconds, making d-feet literally unusable.
This MR fixes this by not allowing a refresh while there is something typed in the search box, and applying the changes when the content in the search box changes.