Forcibly kill bugreports between test cases. This will prevent a failure in one test case from cascading into others and causing flakes. Since only one bugreport can be in progress at once, a test failing to reach the end of its BR may then cause subsequent test cases to receive BUGREPORT_ERROR_ANOTHER_REPORT_IN_PROGRESS. Bug: 179224456 Test: atest CtsCarrierApiTestCases:BugreportManagerTest Change-Id: I8d730d8b1a0f79c1ee536b47d828aa8274af14be