Remove bad error message in glance-cache-manage
Remove bad error message in glance-cache-manage

The error message covering unauthorized requests implies that the
caller hasn't set the appropriate authentication values. What
is more likely is that the values are set but the user just
doesn't have permission to use the tool.

Change-Id: I95f4c1b6fc650b6bf8c11a4e343e1b54c14310f9

darren-wang/gl,redhat-openstack/glance,tanglei528/glance,openstack/glance,paramite/glance,ozamiatin/glance,rickerc/glance_audit,openstack/glance,takeshineshiro/glance,SUSE-Cloud/glance,takeshineshiro/glance,vuntz/glance,ozamiatin/glance,klmitch/glance,saeki-masaki/glance,citrix-openstack-build/glance,klmitch/glance,jumpstarter-io/glance,openstack/glance,rajalokan/glance,jumpstarter-io/glance,ntt-sic/glance,ntt-sic/glance,wkoathp/glance,vuntz/glance,darren-wang/gl,JioCloud/glance,scripnichenko/glance,scripnichenko/glance,akash1808/glance,saeki-masaki/glance,wkoathp/glance,kfwang/Glance-OVA-OVF,sigmavirus24/glance,cloudbau/glance,sigmavirus24/glance,dims/glance,akash1808/glance,citrix-openstack-build/glance,redhat-openstack/glance,cloudbau/glance,stevelle/glance,JioCloud/glance,paramite/glance,tanglei528/glance,dims/glance,stevelle/glance,kfwang/Glance-OVA-OVF,rickerc/glance_audit,rajalokan/glance,SUSE-Cloud/glance