Allow adding a select interface to a selected zone.

[flybyray]

Fixes #4

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name: Pull request
about: Describe the proposed change

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Describe the change
This patch allows to add an interface to a selected zone only on operating systems with firewalld. There is a new list variable firewall_interfaces. Example usage:

- role: ansible-role-firewall
  firewall_interfaces:
    - interface: eth0
      zone: trusted

Testing
Tests where done in a new molecule scenario called physical (maybe rename or remove it if there are better options) only on selected operating systems which might be used with firewalld service.

[dgibbs64]

This is exactly the feature I am after with this role +1 on this feature