Remark: hitting the shutdown option TWICE will ignore the timer and shutdown regarding the timer. That might be another option for you.
See
/etc/acpi/powerbtn.sh
Important part:
# If the current X console user is running a power management daemon that
# handles suspend/resume requests, let them handle policy This is effectively
# the same as 'acpi-support's '/usr/share/acpi-support/policy-funcs' file.
[ -r /usr/share/acpi-support/power-funcs ] && getXconsole
PMS="gnome-settings-daemon kpowersave xfce4-power-manager"
PMS="$PMS guidance-power-manager.py dalston-power-applet"
PMS="$PMS mate-settings-daemon"
PMS="$PMS unity-settings-daemon"
Your might have more options (I checked 16.04.4 server ) It has several options in the to test for different desktops. Assuming you are using systemd: systemd-login uses /etc/systemd/logind.conf for its settings.
[Login]
#NAutoVTs=6
#ReserveVT=6
#KillUserProcesses=no
#KillOnlyUsers=
#KillExcludeUsers=root
#InhibitDelayMaxSec=5
#HandlePowerKey=poweroff
#HandleSuspendKey=suspend
#HandleHibernateKey=hibernate
#HandleLidSwitch=suspend
#HandleLidSwitchDocked=ignore
#PowerKeyIgnoreInhibited=no
#SuspendKeyIgnoreInhibited=no
#HibernateKeyIgnoreInhibited=no
#LidSwitchIgnoreInhibited=yes
#HoldoffTimeoutSec=30s
#IdleAction=ignore
#IdleActionSec=30min
#RuntimeDirectorySize=10%
#RemoveIPC=yes
#UserTasksMax=12288
So I would expect this one:
InhibitDelayMaxSec=
Specifies the maximum time a system shutdown or
sleep request is delayed due to an inhibitor lock of type "delay"
being active before the inhibitor is ignored and the operation
executes anyway. Defaults to 5.