Allow user to specify a full URL with a path for the "auth_url" argument in the
OpenStack driver, add storage driver for KT Ucloud. (LIBCLOUD-431)

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Use ==, use single quotes, remove long comment, this will be moved into
documentation.
lint.
Update CHANGES.
docs: Update OpenStack driver documentation and document how auth_url variable
works. Also update affected code examples.