scope['variable'] for proper variables handling, ldap loop... and some linter stuff

[khdevel]

I found some issues which may be fixed:

• in the templates' files for the services like webserver or worker the syntax for variables is as follow:

@foo

and it seems to be hard to reach them, so I propose to change it to the

scope['airflow::foo']

• also there are some puppet-linter issues like:

$ puppet-lint modules/airflow/manifests/
modules/airflow/manifests//resource/service.pp - WARNING: arrow should be on the right operand's line on line 11
modules/airflow/manifests//params.pp - ERROR: trailing whitespace found on line 75
modules/airflow/manifests//config.pp - WARNING: arrow should be on the right operand's line on line 11

• the celery_ssl_active should be done for an apache-airflow v1.9 It is necessary for proper application setup. My proposition is to set it false by default

• I also see that an airflow.cfg.erb file has static LDAP settings which may be treated more dynamic. I used a loop for it which allows to add some other than listed values like search_scope
  It is for your decission if you like it or not... if yes it may be used in other elements like statsd_settings or mesos_settings

Tested with the apache-airflow v1.9

[khdevel]

@daniran Proposed PR is here: [issue_#6] scope['variable'] for proper variables handling... and some linter stuff