DeviceKeyHandler: Increase handler priority

Allow DeviceKeyHandler to have higher priority when handling user keystrokes.

Patchset 2: Update commit message
Patchset 3: Rebased
Patchset 4: Fixed needed ref
Patchset 5: Rebased

Needed by http://review.cyanogenmod.org/#/c/35064

Change-Id: I60871052aaae0af7d864113f00dbdf9ba5200f2e
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>