Fix live_node_tests

There were a bunch of minor bugs in the live_node_tests. With these changes, all but one test passes, and that test exercises a known bug in Riak KV 2.0pre2. The error should look like:

```
  riakc_pb_socket:3228: live_node_tests (counter increment / decrement / get value)...*failed*
in function riakc_pb_socket:'-live_node_tests/0-fun-139-'/0 (src/riakc_pb_socket.erl, line 3236)
**error:{badmatch,{error,<<"Error processing incoming message: error:undef:[{riak_kv_cou"...>>}}
```