When loopback device is being brought down, then keep the route table
entries because they are special. The entries in the local table for
linklocal routes and ::1 address should not be purged.

This is a sub optimal solution to the problem and should be replaced
by a better fix in future.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>