netinfo: Add 'bootproto4' to all devices

Previously, this information (which deprecated the use of
ifcfg BOOTPROTO property) was added only to devices used by
networks.

By advertising bootproto4 (either "none" or "dhcp")
for all devices, a new scenario is now possible.

When installing a new host, devices now clearly show in their
bootproto4 parameter that they were either configured by dhclient
("dhcp") or their address was set manually ("none"), regardless
of an ifcfg file having been used.

Change-Id: I88e8a4afa7759d37b9bd5c68a18d38baecfe94a6
Bug-Url: https://bugzilla.redhat.com/987813
Signed-off-by: Ondřej Svoboda <osvoboda@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/28592
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>