RX: ignore all local 127/8 IFF_LOOPBACK interfaces

RX: ignore all local 127/8 IFF_LOOPBACK interfaces

Currently RX lists all non-127.0.0.1 interfaces in the interface list,
even those that are specified as IFF_LOOPBACK, to accomodate certain
special cases where IFF_LOOPBACK interfaces should be advertised.
However, this makes us advertise e.g. a 127.0.0.2 lo interface. So
instead, skip all interfaces that are both in 127/8 and claim they are
IFF_LOOPBACK, as this will skip a stray 127.0.0.2, but should not
confuse the special cases.

Change-Id: I60a4ed5330252078e2f58894195f9b68ec70dcfa
Reviewed-on: http://gerrit.openafs.org/2376
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>