don't active the main window if it has other transients when closing a tansient window

Set the newly opened window to be activated in KWin. If an application close the old transient window after opening a new transiwnt window for a short period of time, the new transient window may not be activated. Because when closing a transient window, kwin will activete its main window in Workspace:: activateNextWindow. An example is in mate-terminal， when you open the create new profile window, input profile name and click create profile button, the the create new profile window will be closed and the edit profile window will be opened with inactive state.

So before activating the main window when closing a transient window, need to check whether the main window contains other transient windows. If the main window has other transient windows, do not set the focusCandidate to the main window.

Signed-off-by: Liu Jie liujie01@kylinos.cn