Fix SystemAlarmDispatcherTest on API 29.

* Explicitly sets the BatteryChargingTracker to a `true` state.

Test: Unit tests pass on an emulator in API 29.
Change-Id: I6ff06aa58d56d7d9a83d2c9c3382847973fa38b8

diff --git a/work/workmanager/src/androidTest/java/androidx/work/impl/background/systemalarm/SystemAlarmDispatcherTest.java b/work/workmanager/src/androidTest/java/androidx/work/impl/background/systemalarm/SystemAlarmDispatcherTest.java
index 620307f..95b6d4c 100644
--- a/work/workmanager/src/androidTest/java/androidx/work/impl/background/systemalarm/SystemAlarmDispatcherTest.java
+++ b/work/workmanager/src/androidTest/java/androidx/work/impl/background/systemalarm/SystemAlarmDispatcherTest.java

@@ -567,6 +567,7 @@
 
     @Test
     public void testConstraintsChanged_withFutureWork() throws InterruptedException {
+        when(mBatteryChargingTracker.getInitialState()).thenReturn(true);
         // Use a mocked scheduler in this test.
         Scheduler scheduler = mock(Scheduler.class);
         doCallRealMethod().when(mWorkManager).rescheduleEligibleWork();