Avoid repeated time calls.

Getting the current time is expensive, so only grab it once before we
start looping.

Bug: 167681468
Test: atest com.android.server.job.controllers.TimeControllerTest
Test: atest CtsJobSchedulerTestCases
Change-Id: Ie924881717d0d38656f511e6ec44c580546e8c8d
1 file changed