Update nova docker README for Glance
Update nova docker README for Glance

The README for nova docker driver did not include the update for
Glance. The end user need to update glance-api.conf to make sure
docker images can be saved to Glance.

DocImpact

Change-Id: Id36420f1ce92b1c5e7b01d15704617df0d735aec

gwdg/nova-docker,msrba/nova-docker,godvmxi/nova-docker,Ye-Yong-Chi/nova-docker,stackforge/nova-docker,Ye-Yong-Chi/nova-docker,ggiamarchi/nova-docker,stackforge/nova-docker,mangalaman93/nova-docker,harnesscloud/nova-docker,mangalaman93/nova-docker,godvmxi/nova-docker,devdattakulkarni/nova-docker-1,cloudbase/nova-docker,harnesscloud/nova-docker,cloudbase/nova-docker,devdattakulkarni/nova-docker-1,Juniper/nova-docker,thanhtien522/nova-docker,ggiamarchi/nova-docker,MinmingQian/nova-docker,gwdg/nova-docker,thanhtien522/nova-docker,AlphaStaxLLC/nova-docker,Juniper/nova-docker,msrba/nova-docker,AlphaStaxLLC/nova-docker,MinmingQian/nova-docker