MXS-1938: Log query for inconsistent replies

If a session command produces a different result on the slave than it did
on the master, a warning is logged. This warning now also logs the query
that was being executed to make investigation of the problem easier.

server/core/session_command.cc

@@ -71,6 +71,11 @@ std::string SessionCommand::to_string()
     /** TODO: Create C++ versions of modutil functions  */
     GWBUF *buf = m_buffer.release();
 
+    if (!GWBUF_IS_CONTIGUOUS(buf))
+    {
+        buf = gwbuf_make_contiguous(buf);
+    }
+
     if (modutil_extract_SQL(buf, &sql, &sql_len))
     {
         str.append(sql, sql_len);