Add nimbispam.py

Steal pam.py from RHEL6-STIG

I think RHEL6-STIG itself stole it from an Ansible branch.  We are not
ready to move to Ansible 2.4 yet (due to the RHEL6-STIG role itself),
which has a "pamd" module, which I believe would replace this.

Adding as nimbispam.py to avoid confusion.

v1.3

v1.3 Adds some 2.2 modules

v1.2: Add updated iptables module.

Add the enhanced iptables ansible module with support for flush and policy parameters.