services/keycloak: Update keycloak_swh_setup.py script
Fix call to keycloak_admin.assign_realm_roles after upstream fix (https://github.com/marcospereirampj/python-keycloak/pull/199).
Use constants for swh-web client roles.
Set swh.web.admin.list_deposits swh-web client role to user test.
Migrated from D6531 (view on Phabricator)