remove Debian's 127.0.1.1 entry for fqdn

According to the documentation:
"The Debian Installer creates this entry for a system without a permanent IP address as a workaround for some software (e.g., GNOME) as documented in the bug #316099.".

So it's not needed (or even not acceptable) when a host has IP address assigned.
Maybe it would be better to check if the IP address is assigned and make a decision based on that, but on the other hand, do we really need that check...?