Comment 64 for bug 1232814

Sorry for double posting. I have found a workaround for my machine. Adding all this content to the file /etc/polkit-1/localauthority/90-mandatory.d/com.ubuntu.enable-hibernate.pkla

[Re-enable hibernate by default in upower]
Identity=unix-user:*
Action=org.freedesktop.upower.hibernate
ResultActive=yes

[Re-enable hibernate by default in logind]
Identity=unix-user:*
Action=org.freedesktop.login1.hibernate
ResultActive=yes

[Re-enable hibernate multiple by default in logind]
Identity=unix-user:*
Action=org.freedesktop.login1.hibernate-multiple-sessions
ResultActive=yes

Fixes my issue (apparently, having multiple users available on same machine needs to hibernate them even if they have not logged in)