iproute2 ip link wrapper

Provide a wrapper for iproute2's "ip -d -o link show" (detailed ip
show without line jumps).
This is done by parsing the standard output from executing the above
command and constructing link objects holding all exposed information
(be it generic such as mtu or link kind specific link vlanid)

Apart from fixing the specified bug, it also future proofs netinfo
(and vdsm networking in general) for newer distributions like F20,
which include more input that we were previously not parsing or
parsing badly. As a key addition, it includes link type detection
depending on iproute detailed output when available and falls back
to ethtool output.

Bug-Url: https://bugzilla.redhat.com/1026236
Change-Id: Ibeee70574536e838076704e76f86f2777d5db9b0
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/21054
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>