behavioral change in gnome-shell gnome-3-16 branch.

[Hussam Al-Tayeb <hussam visp net lb>]

Previously if I was logged and I ctrl+alt+f1, gdm would offer to unlock
my session. This was misleading since my session was not really locked.
I could ctrl+alt+f3 and continue working.

After the checkins on 2015-07-24 to gnome-3-16 branch, the behavior
changed. It not longer offers to unlock after ctrl+alt+f1 (which fixes
the misleading behavior or privacy issue).

But if I log on to the same user, it terminates the existing session
and starts a new one without telling me that it terminated the old
session.
Is this intentional?