CTS: Use KEYCODE_WAKEUP/SLEEP instead of KEYCODE_POWER

Behavior of power button maybe overrided per device. Besides,
adding wait time to let states settle before validating triggered.

Test: atest DeviceStatesTest
Change-Id: I3c8172c96ecfcbe616a0bf5c041bffd2259ae4b0
Fix: 80490631
1 file changed