ledflasher: Use lights HAL if it is available.

Change the ledflasher to use the lights hal if it is available. If the
lights hal isn't available, then it defaults back to using sysfs.

Remove a CHECK from ledflasher.cpp as a short term fix. Added a TODO
there for a longer term solution.

BUG=24846780
BUG=25498156
TEST=manual test on both the edison and dragonboard

(cherry picked from http://r.android.com/181007)

Change-Id: Id536c4b44b3f573844451ed257659ca74ac32b00