Replace deprecated check for innodb support

Since MySQL 5.6.1, the server variable `have_innodb` has been removed. The command `SHOW ENGINES` instead is supported since MySQL 4.1.

See http://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_have_innodb
Code style
Merge pull request #663 from jeromegamez/EZP-21006_engine_check

EZP-21006: Mysql >= 5.6.1 - Replace removed check for innodb support through server variables