Serial console fixes

Fix for mira machines serial console and also fixing grub serial
console so the menu actually displays from serial console (as it
originally was broken on plana/burnupi as well).
Change /etc/hosts from 127.0.1.1 to static FRONT ip.

Change the /etc/hosts entry from being like:

127.0.1.1       mira006.front.sepia.ceph.com    mira006

to:

10.214.131.130  mira006.front.sepia.ceph.com    mira006

so that lookups to the the machines own hostname resolve to its
front IP address instead of 127.0.1.1.
Removed networking restart

This is not really needed now that most machines have had
ceph-qa-chef ran on them. Also it runs on them during the end of
the preseed during imaging and they reboot right after that so
there is really no need for it there either. It was only needed
in the first place to deal with machines that did not yet have their
interfaces file updated to have static IPs to take effect immediately.

Signed-off-by: Sandon Van Ness <sandon@inktank.com>
Use DH's irvine NTP appliance instead of debian pool

User DH's NTP appliance in the same DC (Irvine) as the lab for
ntp (time sync) instead of just using the generic debian pools to
try to get more consistent clocks accros the lab.

Signed-off-by: Sandon Van Ness <sandon@inktank.com>