Don't raise MySQL 2013 'Lost connection' errors
Don't raise MySQL 2013 'Lost connection' errors

Although this code error is part of the `ping_listener` tests, it was
missing from the list of known - and ignored - connection errors.

The code error 2013 refers to a connection lost during a query, see:
https://dev.mysql.com/doc/refman/5.0/en/error-messages-client.html#error_cr_server_lost

Without this error code, the session won't try to reconnect to mysql,
which makes `max_retries` useless.

Closes-bug: #1276510
Change-Id: I27cad999b30a480ae23250150bfcba2668acabd7

NaohiroTamura/ironic-lib,faizan-barmawer/elytics,citrix-openstack-build/ironic-lib,openstack/ironic-lib,faizan-barmawer/ironic-lib