Delete unused ContextMiddleware
Delete unused ContextMiddleware

heat.common.context.ContextMiddleware appears to be the only
one that matters

Change-Id: If4166fa75f7179251b132ac6082b7f29d94b6e97

JioCloud/heat,takeshineshiro/heat,dragorosson/heat,srznew/heat,varunarya10/heat,pshchelo/heat,steveb/heat,redhat-openstack/heat,citrix-openstack-build/heat,gonzolino/heat,varunarya10/heat,pshchelo/heat,pratikmallya/heat,takeshineshiro/heat,noironetworks/heat,gonzolino/heat,rdo-management/heat,rickerc/heat_audit,maestro-hybrid-cloud/heat,citrix-openstack-build/heat,pratikmallya/heat,rickerc/heat_audit,ntt-sic/heat,rh-s/heat,rh-s/heat,openstack/heat,rdo-management/heat,steveb/heat,dims/heat,dragorosson/heat,jasondunsmore/heat,JioCloud/heat,miguelgrinberg/heat,openstack/heat,jasondunsmore/heat,miguelgrinberg/heat,redhat-openstack/heat,ntt-sic/heat,NeCTAR-RC/heat,cryptickp/heat,cwolferh/heat-scratch,cryptickp/heat,maestro-hybrid-cloud/heat,cwolferh/heat-scratch,noironetworks/heat,srznew/heat,dims/heat,NeCTAR-RC/heat