ipahost.py

Since ipahost uses dnsrecord-show, it raises an error when DNS zone is
not found, but it should not be an ipahost concern.

This patch fixes this behavior by returning no record if DNS zone is
not found, so processing resumes as if there is no record for the host.
It fixes behavior when `state: absent` and dnszone does not exist, so,
host should not exist either, and the ipahost answer is correct and
indifferent to DNS Zone state.