Don't raise MySQL 2013 'Lost connection' errors

Closes-bug: #1276510

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.

Change-Id: Ie7e3afa121bd7f42c90d20b98b3a83ad40fa8e76