The issue was that the old method simply didn't work. When the hosts
file should look like:
127.0.1.1 host.fqdn.com host
It looked like:
127.0.1.1 host.fqdn.com host old.fqdn.com old
Or this if the user didn't set a fqdn
127.0.1.1 host host old.fqdn.com old
This patch fixes that.
On Debian and Ubuntu guests, when the new hostname of the guest box is
set, the DHCP client (isc-dhcp-client) won't renew its DHCP lease with
the new hostname. Executing "ifdown -a; ifup -a" to reinitialize all auto
interfaces fixes this issue.
Furthermore, as vagrant will now actually wait until a DHCP lease is
acquired, it is guaranteed that the the correct domainname is set from
DHCP before calling other provisioners like puppet, that rely on it.
This fixes puppet/facter sometimes failing to find the fqdn fact on an
LXC guest when the DHCP server is responding too slow.