Comment 3 for bug 1457049

When the problem is present, dm-tool lock is not working, either
While the session flashes briefly without being locked, the output of lightdm.log reads:

[+1156.47s] DEBUG: Seat seat0: Locking
[+1156.47s] DEBUG: Seat seat0: Creating greeter session
[+1156.47s] DEBUG: Seat seat0: Creating display server of type x
[+1156.47s] DEBUG: Using VT 4
[+1156.47s] DEBUG: Seat seat0: Starting local X display on VT 4
[+1156.47s] DEBUG: DisplayServer x-3: Logging to /var/log/lightdm/x-3.log
[+1156.47s] DEBUG: DisplayServer x-3: Writing X server authority to /run/lightdm/root/:3
[+1156.47s] DEBUG: DisplayServer x-3: Launching X Server
[+1156.47s] DEBUG: Launching process 2527: /usr/sbin/X :3 -seat seat0 -auth /run/lightdm/root/:3 -nolisten tcp vt4 -novtswitch
[+1156.47s] DEBUG: DisplayServer x-3: Waiting for ready signal from X server :3