bondOpts: Fix reporting [] instead of [''] for empty opts

Touched also speed so that it would not try to access the first
element of what is not an empty list instead of a list with an
empty element.

Change-Id: I20963543ec6b0f9ff42c02431ec9758d7de0531e
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/21554
Reviewed-by: Dan Kenigsberg <danken@redhat.com>