Fix testDeviceStateChanges fail.

Request device_state_change will post to work thread and return.If dump statsd immediately,there is a race-condition,maybe get a null statsd report cause test fail.

Bug: 243122614
Test: run cts -m CtsStatsdAtomHostTestCases -t android.cts.statsdatom.devicestate.DeviceStateStatsTests#testDeviceStateChanges
Change-Id: Ifc6d907c1e487ea8d42156a00bbf1896f765b467
(cherry picked from commit 003c66e9e615a86c0bd1f5679faa32fcd384f689)