Updates reportChooserSelection to be synchronized with queryUsageStats

in UsageStatsService, to fix a flaky test.

Bug: 35763877
Test: manually ran the flaky tests for 50 times, to verify that it is
stable.

Change-Id: I56d355bb283275f33bf7a24d0cc5b6454b99a35e
(cherry picked from commit 434f76a8)