Docker: Reset minimum autotest version

Formerly, the version set could not be reached from current
HEAD for whatever reason (non-ff update maybe?).  Reset
the minimum default reference to one currently reachable.

Signed-off-by: Chris Evich <cevich@redhat.com>
Merge pull request #208 from cevich/def_ver

Docker: Reset minimum autotest version
dockertest.images: Switch to TextTable

Switch to using output.TextTable to parse
docker images output.  This is for consistency
with containers module and to help verify
header-column widths always matches content widths.

Also added ``images_args`` attribute in case
instances need to pass more/different arguments
than just ``--no-trunc``.  Removed a no-longer
relevant FIXME.

Signed-off-by: Chris Evich <cevich@redhat.com>