Hide overview after "switch user" action

For better user experience, show plain desktop instead opened overview
after "switch user" action.

GNOME/gnome-shell!543
4 jobs for !543 with switch-user-close-overview in 3 minutes and 36 seconds (queued for 1 second)
latest detached
Status Job ID Name Coverage
  Review
passed #298097
check_commit_log

00:00:32

 
  Build
passed #298098
build

00:02:10

 
  Test
passed #298099
test

00:00:53

passed #298100
test-pot

00:00:43