Reset TimeZone default before each test

The CtsTestRunner already resets various static values between
tests to limit test "leakage". TimeZone is notably absent in
CTS (though not vogar). This change allows tests to rely on
the test infrastructure to reset the TimeZone between tests.

Change-Id: Id6825178b04a429c92841ab27f26e1dcbc66c3cc
1 file changed