Comment 2 for bug 1630299

Problem description:

1) node-A gets IP x.x.x.x
2) node-A reports IP x.x.x.x to nailgun and it's saved to DB
3) node-A goes offline (or DHCPREQUEST/DHCPACK packets are lost during IP lease renewal)
4) DHCP lease for IP x.x.x.x expires
5) node-B gets IP x.x.x.x
6) node-B reports IP x.x.x.x to nailgun and it's saved to DB (here we have duplicate IPs in DB)
7) deployment task is started where node-A and node-B have the same x.x.x.x IP
9) provisioning fails with error:
#<XMLRPC::FaultException: <class 'cobbler.cexceptions.CX'>:'IP address duplicated: x.x.x.x'>

Simple solution:
Increase DHCP lease time up to several days (average time between bootstrap of first nodes and provisioning step)

Complex solution (new fuel feature):
Update MAC<-->IP pinning in Cobbler/DHCP as soon as node (mac, IP) is updated in the DB, not only on provision step as we do now. This way we won't have "split brain" information on MAC<-->IP mappings.