window: Add user_op parameter to update_monitor()

When workspaces-only-on-primary is set and a window is moved back to the
primary, we also move it to the active workspace to avoid the confusion
of a visible window suddenly disappearing when crossing the monitor border.
However when the window is not actually moved by the user, preserving the
workspace makes more sense - we already do this in some cases (e.g. when
moving between primary monitors), but miss others (unplugging the previous
monitor); just add an explicit user_op parameter as used elsewhere to cover
all exceptions.

https://bugzilla.gnome.org/show_bug.cgi?id=731760

src/core/window-private.h

@@ -690,7 +690,8 @@ void meta_window_activate_full (MetaWindow     *window,
 
 gboolean meta_window_is_client_decorated (MetaWindow *window);
 
-void meta_window_update_monitor (MetaWindow *window);
+void meta_window_update_monitor (MetaWindow *window,
+                                 gboolean    user_op);
 
 void meta_window_set_urgent (MetaWindow *window,
                              gboolean    urgent);