Remove unnecessary getpriority() system call

This was introduced for a valid reason in aosp/1224543, but that reason
was later removed. This code wasn't.

It is not worth making a system call in order to possibly avoid a second
one, which I expect is no more expensive in that, particularly easy,
case.

Test: Treehugger
Change-Id: I346f9b641c6feb791247b16fb900a4ad97e646d2