baremetal element: Enable stable interface names

By default most cloud images have disabled the
udev rules which give us stable network interface names. While
this is a reasonable default for something like EC2 (the target
for these images) this is very bad behavour on bare metal
and can cause a "musical NICs" situation to occur where
on reboot the NIC names get swapped.

In this commit we re-enable stable interface naming by
removing the dev nulled rules softlink and installing
the biosdevname package. Once this is done interface
names should again show up as em1, em2 instead of
the old eth0, eth1.

We also remove some the common, statically configured
eth0 config files on some distributions. Equivalent
files (if needed) may be auto-generated by using
the dhcp-all-interfaces element.

Change-Id: Idd67977342719e2f295e2fa2c0ed6cfa8602171a