Avoid blinking buttons by not re-instanciating the workspace buttons when refreshing the GUI

[vxgmichel]

A lot of events trigger a refresh of the workspaces widget, which causes the workspace buttons widget to be re-instantiated often. The problem is that this discards the previous state of the button, meaning the different piece of information have to be fetched and set again. But the fetch operation might be a trio job that will only produce the correct information later. This causes some buttons such as the re-encryption button to blink when the interface is refreshed.