* Check that verify_ssl defined in tower_cli.cfg isn't ignored
* Avoid to override verify_ssl value defined in tower_cli.cfg
By default, tower-cli library enables SSL certificates check. But
verify_ssl false value defined in config files read by default by
tower-cli library (for example /etc/tower/tower_cli.cfg) was ignored
because overriden by the tower_verify_ssl parameter default value.
* fix a typo in comment
