When "Grab Keys" is enable, override application shortcuts; BUG: 496692
When working on a remote session it's common to use keyboard shortcuts, eg. ctrl+w to close a remote browser tab. Krdc itself defines some application shortcuts in its default configuration, es ctrl+w to close the current connection tab. This MR overrides application shortcuts when "grab keys" is enabled, so that the shortcut keys are sent to the remote session.