Updates default --sort behaviour
Updates default --sort behaviour

When querying against a Juno glance-registry, we found that having the
--sort option defaulting to 'name:asc" results in querying the registry
with additional SQL parameters like the following:

WHERE image_properties_2.name = :name_1 AND image_properties_2.value =
:value_1

as a result of handling the newer 'sort' filter. This results in a
blank list being returned as the output of glance image-list.

This patch sets the --sort-key and --sort-dir instead of --sort when
neither --sort-key nor --sort-dir are specified, so as to maintain
backwards compatibility with Juno glance-registry.

Change-Id: I8bd64cca7f1b7abdbabf4c09e3dbbcb4044e51b4
Closes-bug: #1492887

klmitch/python-glanceclient,openstack/python-glanceclient,klmitch/python-glanceclient,openstack/python-glanceclient