If e.g the ambassador service annotation points to an nonexisting service, external-dns will not update any DNS records. This PR makes external-dns ignore the host and carry on instead.
Ambassador can be configured with `Host` resources (based on the
`Host` CRD) for defining the external DNS host name.
This code adds a new source, `ambassador-host`, that looks for the
`ambassador/ambassador` Service and and uses the `hostname` from the
`Host` resource.
Signed-off-by: Alvaro Saurin <alvaro.saurin@gmail.com>
Signed-off-by: Flynn <flynn@datawire.io>
