base: fixed offscreen volume key handling

http://jira.omnirom.org/browse/OMNI-757

Dont handle up and down

Change-Id: I2b073aa2aef2fa671071257521b906dd6fddfb3c
Merge "base: fixed offscreen volume key handling" into android-4.4
Merge pull request #12 from omnirom/android-4.4

merge