Add baremetal support for install gather

[stbenjam]

openshift added debugging - https://github.com/openshift/installer/blob/master/cmd/openshift-install/gather.go - on installation failure. We need to add support for the baremetal platform. In order to do that, terraform needs to know the IP's of the bootstrap and master nodes.

This produces some confusing error messages:

level=debug msg="Fetching \"Install Config\"..."
level=debug msg="Loading \"Install Config\"..."
level=debug msg="  Loading \"SSH Key\"..."
level=debug msg="  Loading \"Base Domain\"..."
level=debug msg="    Loading \"Platform\"..."
level=debug msg="  Loading \"Cluster Name\"..."
level=debug msg="    Loading \"Base Domain\"..."
level=debug msg="  Loading \"Pull Secret\"..."
level=debug msg="  Loading \"Platform\"..."
level=debug msg="Using \"Install Config\" loaded from state file"
level=debug msg="Reusing previously-fetched \"Install Config\""
level=error msg="Cannot fetch the bootstrap and control plane host addresses from state file for baremetal platform"
level=error msg="boostrap host address and at least one control plane host address must be provided"

This isn't the actual failure, it's just a failure to gather debugging data. The real problem should be elsewhere in the log (usually a timeout)

[stbenjam]

For the masters, we will be able to gather the IP's via introspection data: openshift-metal3/terraform-provider-ironic#28

[russellb]

replaced by openshift/installer#2009