include the dns_infrastructure_key in oo_instrastructure.conf

@ekohl nsupdate changes would affect the oo_infrastructure.db file, which is still listed as replace => false.

Allowing oo_infrastructure.conf to be replaced allows the user to update the infrastructure key after the fact.  It would also allow anyone that previously installed openshift using the puppet module to pick up the change that fixes oo_infrastructure.conf to include the infrastructure key.

The user could potentially shoot themselves in the foot by changing the infrastructure zone after the fact, but I think allowing the user to update the key would be enough value to offset the danger.