stop memoizing on request argument in cinder api
stop memoizing on request argument in cinder api

cinder api should memoize more persistanly on objects that do not
change when rendering each view, i.e. Supported extensions list

Implements blueprint: improve-horizon-caching

Change-Id: I3939f2a09b19cc2715738b8dbedc13606b2430dc

BiznetGIO/horizon,noironetworks/horizon,noironetworks/horizon,NeCTAR-RC/horizon,NeCTAR-RC/horizon,yeming233/horizon,sandvine/horizon,NeCTAR-RC/horizon,bac/horizon,yeming233/horizon,BiznetGIO/horizon,coreycb/horizon,openstack/horizon,openstack/horizon,wolverineav/horizon,sandvine/horizon,ChameleonCloud/horizon,BiznetGIO/horizon,NeCTAR-RC/horizon,coreycb/horizon,sandvine/horizon,wolverineav/horizon,BiznetGIO/horizon,bac/horizon,coreycb/horizon,bac/horizon,noironetworks/horizon,yeming233/horizon,bac/horizon,wolverineav/horizon,wolverineav/horizon,ChameleonCloud/horizon,coreycb/horizon,sandvine/horizon,noironetworks/horizon,ChameleonCloud/horizon,openstack/horizon,yeming233/horizon,ChameleonCloud/horizon,openstack/horizon