Add support for custom list of Ansible Controllers

DebOps playbook manages to remote hosts automatically using
'ansible_controller' variable, checked at startup. But if
'debops.tcpwrappers' role is used standalone, this check cannot be
performed automatically. Because of that, you can now define a list of
CIDR hosts in 'tcpwrappers_ansible_controllers' variable to specify list
of hosts and networks allowed to connect to 'sshd' service without
restrictions.