differentiate between client vs. server errors in InfluxDbException

[jack-kerouac]

When dealing with an InfluxDbException, it would be useful to know whether the HTTP error code was 4xx, indicating a problem with the client, e.g. an invalid query, or whether it was a 5xx error, indicating a problem with the server.

Currently, these cases cannot be differentiated. This is important for us, because we are using Hystrix and would only like to count 5xx failures against the metrics for the circuit breaker.

[majst01]

OK, this would require some refactoring of the code talking to influxdb. If you have some ideas howto differentiate, your are welcome to show this in a PR.

[dubsky]

This has been already done in #410. See InfluxDBException.isRetryWorth()