In some cases, for example when the instance does not have internet
access, or to speed up slapos node instance, it's better not to have
frontend requests in the embedded slapos. In this case, the default
slapos proxy behavior of returning a "fake frontend" [1] will apply
and promises checking frontend status will pass anyway.

This change does not apply automatically after updating existing
instances, it is necessary to restart the embedded slapos proxy after
update, by running:

    supervisorctl -c ~/srv/runner/etc/supervisord.conf restart slapos-proxy

[1]: see slapos.core commit 2a53efca2 (proxy: bypass simple fronten
requests by returning URL, 2019-03-25)