login as different user broken - 17.04

[amykyta3]

Two issues, likely related

Setup:
Ubuntu GNOME 17.04
I have two user accounts on this machine "A" and "B"
Machine logs into "A" by default.

Logout hangs
When logging out of a user A's session, screen goes black. Does not show user list login screen.

Switch user via lock screen broken

1. Start in user A session
2. Explicitly lock the session via user menu
3. At lock screen, select "login as different user"
4. Instead of presenting the user list, user A's session is immediately resumed, amusingly bypassing the password.

Confirmed that uninstalling this extension fixes both issues.