make uploading an image as public admin only by default
make uploading an image as public admin only by default

Uploading an image with --is-public=True should by default only be allowed
by an admin tenant. Allowing anyone to upload an image as is_public is likely
a security concern. This changes the previous default behavior glance had
of allowing anyone to upload an image as is_public previously by default.

DocImpact
Closes-bug: 1317314

Change-Id: I60d2257115e9207e09b50d9f950076b7fe8237d7

openstack/glance,dims/glance,openstack/glance,sigmavirus24/glance,ozamiatin/glance,vuntz/glance,redhat-openstack/glance,darren-wang/gl,takeshineshiro/glance,redhat-openstack/glance,JioCloud/glance,dims/glance,takeshineshiro/glance,paramite/glance,rajalokan/glance,scripnichenko/glance,paramite/glance,tanglei528/glance,jumpstarter-io/glance,darren-wang/gl,klmitch/glance,rajalokan/glance,JioCloud/glance,wkoathp/glance,stevelle/glance,vuntz/glance,kfwang/Glance-OVA-OVF,ozamiatin/glance,stevelle/glance,saeki-masaki/glance,tanglei528/glance,scripnichenko/glance,klmitch/glance,saeki-masaki/glance,jumpstarter-io/glance,akash1808/glance,openstack/glance,wkoathp/glance,kfwang/Glance-OVA-OVF,akash1808/glance,sigmavirus24/glance