packaging: setup: allow invalid fqdn in non interactive mode

in interactive mode we allow user to retry and correct invalid host
name, in non interactive mode we simply fail installation.

there are two reasons why we should not fail installation:

1. in upgrade we need to accept whatever host name existed during setup.
   this is easy to solve by activating validation only for setup.

2. user who specify host name via cmd-line should know what he is doing,
   we cannot enforce our decision over.

this change will produce error during non interactive setup, but will
allow setup to continue.

Change-Id: Ic6c80ac47d55ade01dd6a3472e950d2c0ffa0074
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>
Reported-By: Michael Pasternak <mpastern@redhat.com>