Refine set_sched_policy behavior

If a thread priority is greater than or equal to
ANDROID_PRIORITY_BACKGROUND, and the new priority is less than
ANDROID_PRIORITY_BACKGROUND, set the sched policy to its parent process.

Bug: 139521784
Test: functionality verified
Change-Id: Ie6fe33e08e4fda0a119b9869e8dd1733c164d79e
1 file changed