on client.py reverse of simple-sso-authorize was not being performed

[ralequi]

2 of 3 of the server endpoints uses "reverse" functionality from the client pathing. However, the path at simple-sso-authorize was hardcoded. I've fixed that is this commit.

This is required when a path-name change is performed, such as:

# ...
sso_cli = Client()
# ... url.py ...
re_path(r'^login/sso/', include(sso_cli.get_urls())),
# ...