Fix out-of-bounds read on invalid query message

When the parsing of a query failed, the message would treat the parameter
as a string as the printf format was `%*s` instead of `%.*s`.

The manpage of printf states the following about the precision specifier:

    ... or the maximum number of characters to be printed from a string
        for `s` and `S` conversions.

This means that the field length specifier is somewhat meaningless for
strings.

query_classifier/qc_sqlite/qc_sqlite.cc

@@ -3603,7 +3603,7 @@ static void log_invalid_data(GWBUF* query, const char* message)
                 length = (int)GWBUF_LENGTH(query) - MYSQL_HEADER_LEN - 1;
             }
 
-            MXS_INFO("Parsing the query failed, %s: %*s", message, length, sql);
+            MXS_INFO("Parsing the query failed, %s: %.*s", message, length, sql);
         }
     }
 }