For example there is no slaptap under StandaloneSlapOS and <RU>-netconf-socket
promise needs real RU hardware to be around and accepting incoming connections.

If we don't wrap such things with `if not testing` running test on testnodes will fail.

/cc @lu.xu, @tomo, @xavier_thompson, @Daetalus
/reviewed-by @jhuge
/reviewed-on nexedi/slapos!1514