netinfo: Hacked InfiniBand speed.

Currently, the kernel errors out with EINVAL when
reading the speed of ib* devices. Report a speed
of 10000 for them.

Handle dummy devices' IOError gracefully.

Change-Id: I55089558d59d33da7f44a2f6d7059d291c064f8a
Bug-Url: https://bugzilla.redhat.com/1103469
Signed-off-by: Ondřej Svoboda <osvoboda@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/28502
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>