MXS-1896: Distinct LOAD DATA LOCAL INFILE from LOAD DATA INFILE

The two operations return different types of results and need to be
treated differently in order for them to be handled correctly in 2.2.

This fixes the unexpected internal state errors that happened in all 2.2
versions due to a wrong assumption made by readwritesplit. This fix is not
necessary for newer versions as the LOAD DATA LOCAL INFILE processing is
done with a simpler, and more robust, method.

server/core/query_classifier.cc

@@ -389,6 +389,9 @@ const char* qc_op_to_string(qc_query_op_t op)
     case QUERY_OP_LOAD:
         return "QUERY_OP_LOAD";
 
+    case QUERY_OP_LOAD_LOCAL:
+        return "QUERY_OP_LOAD_LOCAL";
+
     case QUERY_OP_REVOKE:
         return "QUERY_OP_REVOKE";