[RESTRICT AUTOMERGE]: Fix a race condition in the crash reporter

problems fixed:
* logcat wasn't cleared before checking for crashes
* unrelated crashes could be reported as part of the current test
* The test could start before the reporter was started
* matching a crash before the test start caused a nullpointerexception

Bug: 162378163
Test: adb shell kill -11 mediaextractor # during run for StagefrightTests
Change-Id: Ie31d1f47c3485808a89c4b33addd303914cb36a4
1 file changed