When multiple interfaces are configured with DHCP, and more than
one interface receives a gateway from the DHCP server(s), the
resulting default gateway on the system is unpredictable. This
change adds the "defroute" boolean to the configuration syntax
for os-net-config. Any interface type may be marked so that the
gateway received from the DHCP server will not be eligible as a
default gateway for the system. This only works for ifcfg files,
/etc/network/interfaces lacks an equivalent option.
Change-Id: Id775f3506b2ec60c9a2833efd49fb8319151c00d
Closes-Bug: 1449288
fa4966f4db