connection possibly staying in hanging state after batch execution

from https://github.com/mariadb-corporation/mariadb-connector-nodejs/issues/281

When using batch and using bulk:
In order to prevent sending a packet with size > max_allowed_packet, with server killing the connection, node.js client test check that bunch of parameter size < max_allowed_packet, and throw a client error in place of executing the command, killing the connection.

This test is incorrectly implemented, leaving sometime the connection in a hanging state