Allow to use relative redirect URIs

[mwperina]

[SSO_ALTERNATE_ENGINE_FQDNS|https://github.com/oVirt/ovirt-engine/blob/master/packaging/services/ovirt-engine/ovirt-engine.conf.in#L492] are not supported with Keycloak, but maybe using relative redirect URI can provide the similar functionality to allow using different than default FQDN and/or port:

OpenIDC/mod_auth_openidc#259

[didib]

This affects also hosted-engine --deploy, as reported on the list:

https://lists.ovirt.org/archives/list/users@ovirt.org/thread/VO4UZALOVRW7VCAEBHAKALQE34PHO5W2/
https://lists.ovirt.org/archives/list/users@ovirt.org/message/OYO6JQT6XKKYTPD7QE7T5GVGEMDNRBEK/

[denvist]

This PR resolve this issue — oVirt/ovirt-ansible-collection#754