Reduce min time to alarm.

Reduce the minimum amount of time needed before the next AlarmClock
before the device will go into Doze from 60 minutes to 30 minutes. If
we're this close to an AlarmClock, AlarmManager will wake the device
from idle 0-15 minutes before the AlarmClock, so going into Doze even
30 minutes before will give the device 15-30 minutes of Doze time.

Bug: 149341011
Test: atest FrameworksMockingServicesTests:DeviceIdleControllerTest
Change-Id: I259e930f86ff1a8708c1be9c4b42f435ceef73b5