deploy/reap.py: Dump extra interfaces information.

deploy/reap.py: Dump extra interfaces information.

Since on AArch64, Ubuntu local mirror lacks arm64 packages (see [1]),
Fuel master requires internet connectivity during deploy, and hence
a way to setup such a public (extra) interface automatically.

Previous commit "transplant: Generate extra interfaces config file"
introduced support for passing this information via DEA (override),
which may define a IFCGF_<interface> section in its 'fuel:'
section, containing the necessary keys to produce a ifcfg-<interface>
file, like in this example:

fuel:
   IFCFG_ETH1:
     device: eth1
     ipaddress: 10.0.1.10
     netmask: 255.255.255.0
     gateway: 10.0.1.254

In order for Network Manager to use the newly added interfaces
for outgoing traffic and honor their GATEWAY setting (e.g. if we just
added one public interface), the default route on admin iface (most of
the time called eth0) is disabled when extra interfaces are present.

FIXME: Only supports lowercase interface names, but so does Fuel,
see related bug report [2].

[1] https://jira.opnfv.org/browse/ARMBAND-35
[2] https://jira.opnfv.org/browse/FUEL-136

Change-Id: Idd6fe95a5a73ec172eca17cfd96f23b1a1bc2bee
Signed-off-by: Alexandu Avadanii <alexandru.avadanii@enea.com>
Signed-off-by: Josep Puigdemont <josep.puigdemont@enea.com>