Remove the prctl PR_SET_TIMERSLACK_PID call.

This is broken on all devices other than N9, and has no real path to fixing
it because there are so many different values already in use (41, 43, 47,
127), with no way to tell which you should use on any given device.

Bug: http://b/30597190
Change-Id: I07eeaaf6f5dc03c5532ffbfbb85ef2ad750206a0