pass additional ANSIBLE_ environment variables to the ansible executor

[lukashartl]

It is possible to change Ansible settings via either ansible.cfg, passing them as command line arguments, passing them as extra variables or via environment variables.

Let's take ANSIBLE_HOST_KEY_CHECKING as an example.
Unfortunately, it can only be set as either:

• Environment Variable: currently not supported by the rundeck plugin
• via ansible.cfg: this variable is only necessary for a single job. And as the name implies, it should only be used on very special occasions.

Unfortunately Rundeck's options also don't help us here, as it is not possible to expose a variable name like ANSIBLE_HOST_KEY_CHECKING to the environment of ansible.

I think that would be a great improvement for the plugin. I would also be happy to help with the implementation.