Switch to use configure_keystone_authtoken_middleware in devstack plugin
Switch to use configure_keystone_authtoken_middleware in devstack plugin

Function "configure_auth_token_middleware" was deprecated in devstack
in [1].
Patch [1] also introduced regression which cause failures in neutron's
neutron-tempest-plugin-designate-scenario job.

New function configure_keystone_authtoken_middleware should be used
instead.
This patch switches to use this new function to solve problem
caused by patch [1] when old function is used.

[1] https://review.opendev.org/#/c/628651/

Change-Id: I96d69bc7a1489377b5e95965e95dc3d3f2f3a933
Closes-Bug: #1834849

mahak/neutron,mahak/neutron,mahak/neutron,openstack/neutron,openstack/neutron,openstack/neutron