Support fernet token provider
Support fernet token provider

Keystone added the "fernet" token provider in Kilo. This adds
support for it.

Change-Id: I6b7342ea67157a40edc8b9ba3d84d118e39d86ed

bigswitch/devstack,olivierlemasle/devstack,mc2014/devstack,group-policy/devstack,pombredanne/devstack,samgoon/devstack,pczerkas/devstack,eharney/devstack,TwinkleChawla/devstack,openstack-dev/devstack,costingalan/devstack,dtroyer/devstack,HPCHub/devstack,TwinkleChawla/devstack,noironetworks/devstack,upadhyay-prashant/devstack,dirkmueller/devstack,Mahito/devstack,dirkmueller/devstack,mssumanth/devstack,pacinete/devstack,prithivm/branch01,dtroyer/devstack,vishnugonela/devstack,pczerkas/devstack,atulpatil301/devstack,mmasaki/devstack,wenhuizhang/devstack,thomasem/devstack,wenhuizhang/devstack,flavio-fernandes/devstack,nawawi/openstack,eharney/devstack,bswartz/devstack,bq-xiao/devstack,varunarya10/devstack,prithivm/branch01,NaokiMiyata/devstack,samgoon/devstack,parul24/devstack,NaokiMiyata/devstack,vishnugonela/devstack,pombredanne/devstack,pacinete/devstack,herrsechs/devstack,ozamiatin/devstack,vsham20/devstack,avvocatodemarchis/devstack,vsham20/devstack,upadhyay-prashant/devstack,parul24/devstack,bq-xiao/devstack,noironetworks/devstack,mc2014/devstack,liuquansheng47/devstack,HPCHub/devstack,mmasaki/devstack,group-policy/devstack,olivierlemasle/devstack,openstack-dev/devstack,richliu/devstack,mssumanth/devstack,herrsechs/devstack,flavio-fernandes/devstack,bswartz/devstack,liuquansheng47/devstack,thomasem/devstack,bigswitch/devstack,ozamiatin/devstack,Mahito/devstack,avvocatodemarchis/devstack,varunarya10/devstack,atulpatil301/devstack,costingalan/devstack,richliu/devstack,nawawi/openstack