Remove transition submode immediately after system state change

Delaying the end of transition submode can cause problems if other
processes use system state change as trigger for making display
state requests etc to mce.
Disable tklock manipulation via power key in act dead

The acting dead ui does not support tklock D-Bus IPC, so it will fail
and cause display blanking as a side effect.
Act on system state change when transition submode ends

Old code triggered also on entry to transition submode, which caused
unwanted screen blanking when going from ACT_DEAD to USER mode.
Fix whitespace
Merge pull request #64 from spiiroin/display_handling_in_act_dead

Fixes to display handling in act dead