desktop-shell: Reject window move in common_surface_move()

We move the check for shsurf->grabbed from surface_move() and
surface_touch_move() up top common_surface_move()
diff --git a/desktop-shell/shell.c b/desktop-shell/shell.c
index 82d8166..9340b4a 100644
--- a/desktop-shell/shell.c
+++ b/desktop-shell/shell.c
@@ -1436,8 +1436,6 @@
 
 	if (shsurf->state.fullscreen)
 		return 0;
-	if (shsurf->grabbed)
-		return 0;
 
 	move = malloc(sizeof *move);
 	if (!move)
@@ -1522,8 +1520,6 @@
 	if (!shsurf)
 		return -1;
 
-	if (shsurf->grabbed)
-		return 0;
 	if (shsurf->state.fullscreen || shsurf->state.maximized)
 		return 0;
 
@@ -1550,6 +1546,9 @@
 	struct shell_surface *shsurf = wl_resource_get_user_data(resource);
 	struct weston_surface *surface;
 
+	if (shsurf->grabbed)
+		return;
+
 	if (seat->pointer &&
 	    seat->pointer->focus &&
 	    seat->pointer->button_count > 0 &&