Move resolv.conf to nailgun host role, dnsmasq.upstream to cobbler

This reverses some previously hardcoded
values for resolv.conf and dnsmasq.upstream
where they had assumed values during OS
installation. DHCP hooks are moved back
to the nailgun::host role so that when the
host gets a DHCP lease, it does not
overwrite /etc/resolv.conf

blueprint fuel-containerizatoin-of-services

Change-Id: I30bc2b5590530fbdf51059b11434ffcdd8b5f3de
Merge "Move resolv.conf to nailgun host role, dnsmasq.upstream to cobbler"