[X11] ignore _NET_WM_MOVERESIZE event if mouse left button is not pressed

Summary: First, we simulate a special case: pause a CSD client process, and then click the title bar to drag. At this time, the client does not move. Then resume the process, move the mouse over the client , and you will find that the client moves with the mouse.In fact, if we install kwin on a virtual machine and access it through cloud desktop. This often happens because a potential race between _NET_WM_MOVERESIZE and mouse event.So,checking mouse left button to avoid window move with mouse