control: Add power on/off triggers

Add two new classes of triggers: powerOn and powerOff.  They are only
called during the power on and power off state changes, respectively.

They behave the same as the existing init trigger.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I9d39210843192b9c343c7838c604fcce7c8d3f3d
4 files changed