LDAP idempotent

With last fix if you try to run the playbook again no changes happen
because there is a check before every step to evaluate the current status
of the remote machine.

If the remote machine is installed, even it is differently configured, there should
not be changes, although in some special condition it could happen
Fixed the firewall error
Merge pull request #39 from INFN-Catania/master

LDAP idempotent