Make `wait_for_any_log()` function to work closer to the original
dtest's version: use `ScyllaLogFile.grep()` method instead of
the usage of `ScyllaNode.wait_log_for()` with a small timeout to
have at least one try to find.
Also, add `max_count` argument to `.grep()` method for the
optimization purpose.
e30e2345b7