Fix how to add a module

The public doc (https://access.redhat.com/documentation/en-us/red_hat_single_sign-on/7.6/html-single/server_installation_and_configuration_guide/index#packaging_the_jdbc_driver)

guides to make a directory and store a jar and module.xml to add a jdbc driver as a module. But it is not a good idea.

It should be added `module add` command via jboss-cli.