boxpointer: Disable offscreen redirect for popup menus

The ClutterOffscreenEffect has a weird bug that lately appears very
often in multi monitor setups, this bug causes the culling checks to
return that the actor isn't on stage and therefore shouldn't be painted.

This obviously causes visual issues and can lead to the popup menus
being completely unusable. To work around this bug until the root cause
is found, disable the offscreen effect for popup menus for now.

Fixes GNOME/gnome-shell#1049
Fixes GNOME/gnome-shell#724

GNOME/gnome-shell!459
4 jobs for !459 with disable-popup-menu-offscreen-redirect in 7 minutes and 11 seconds (queued for 2 seconds)
latest detached
Status Job ID Name Coverage
  Review
passed #245274
check_commit_log

00:03:33

 
  Build
passed #245275
build

00:02:17

 
  Test
passed #245276
test

00:01:19

passed #245277
test-pot

00:01:19