Allow `--force-join` option to be configured via class parameter
* Allow using an option to override client's entry and force enrollment + `ipa-client-install` can use "--force-join" option to override the host entry on the server and force client enrollment. + $freeipa::force_join sets $client_install_cmd_opts_force_join - it checks if you want to use that option or not; - should you do, we introduce it to $client_install_cmd * Present $client_install_cmd_opts_force_join to `ipa-client-install` * Referency information about "force_join" option and its default value * Document @force_join parameter and what the default behavior is * Officially introduce `@force_join` into a Puppet manifest