Riak TS may return msg code 0 even when TTB specified [JIRA: CLIENTS-839]

[lukebakken]

Test:

• Enable Riak Security
• Try a Riak TS Query using TTB, but don't specify auth or to use security
• Riak will return msg code 0 and the "please STARTTLS message" in a PB-encoded RiakError

[alexmoore]

We handle this in the Java client already, we read the reply message code and act according to that instead of expecting one format or another.