nit_fb: defer mode change to client response

The '_active_mode' must not be changed at any time except when the
client asks for the 'Framebuffer::mode'. Otherwise, the dimensions of
dataspace used by the client is not always consistent with the mode
information as gathered by the client.

repos/os/src/server/nit_fb/main.cc

@@ -377,12 +377,6 @@ struct Nit_fb::Main : View_updater
 		}
 
 		fb_session.size(Area(width, height));
-
-		/*
-		 * Simulate a client call Framebuffer::Session::mode to make the
-		 * initial mode the active mode.
-		 */
-		fb_session.mode();
 	}
 
 	void handle_config_update()