Revert "Switch fernet to be the default token provider"
Revert "Switch fernet to be the default token provider"

This reverts commit 181588b9ba50fefea12617a9a5e774daddfed20c.

Since this change landed on 4/29 it's been the cause of the
top two gate failures (besides known latent infra issues) and
hasn't had good progress on landing a fix, so until it's a
priority for the keystone team we need to revert this change
to get the integrated gate jobs moving again.

Change-Id: I588a84c5179eab072d21bc1394aea2df00929650
Related-Bug: #1577558
Related-Bug: #1578866

bswartz/devstack,dtroyer/devstack,nawawi/openstack,noironetworks/devstack,Mahito/devstack,dtroyer/devstack,bswartz/devstack,richliu/devstack,bigswitch/devstack,openstack-dev/devstack,richliu/devstack,noironetworks/devstack,openstack-dev/devstack,group-policy/devstack,Mahito/devstack,bigswitch/devstack,group-policy/devstack,nawawi/openstack