The test following test is flaky:
TEST_ASSERT(msg->send_time > 0U);
It assumes that 0 as time is indicating the time is invalid. But on
`native`, the time will be zero for the first millisecond the test
is launched. Before the interactive sync caused seemingly a reliable
delay of at least one milli second, but this no longer is the case.
This works around the bug by just waiting at the start of the test
until the time is no longer zero, possibly spinning for one millisecond.
