sync_with_ping currently returns false if the timeout expires, and it is
the caller's responsibility to fail the test. However, none of the tests
currently assert on sync_with_ping()'s return code. This commit adds an
assert to sync_with_ping so the test will fail if the timeout expires.
This commit also removes all the duplicate implementations of
sync_with_ping() from the individual tests.
6a18bb9a36