Fix url in list_services
Fix url in list_services

This commit fixes list_services by changing the url passed to self.get
from 'services' to url, because url can concatenate **params
to 'services'.

Change-Id: I2e2ebb72732ab95d5f9c1d988037c5e263bf2a71

Juniper/tempest,Juniper/tempest,masayukig/tempest,openstack/tempest,cisco-openstack/tempest,masayukig/tempest,vedujoshi/tempest,vedujoshi/tempest,openstack/tempest,cisco-openstack/tempest