Default to single-version-externally-managed
Default to single-version-externally-managed

The other thing is always confusing and never what people want.

Change-Id: I915f561da2f74048c24dd324dbe71b5446d39197
Reviewed-on: https://review.openstack.org/28060
Reviewed-by: James E. Blair <e81a02a9d6405977f63a769d9f6ec8ed9d924325@inaugust.com>
Reviewed-by: Clark Boylan <635fc31d01fa593720982fa0568e87170cedbe2c@gmail.com>
Approved: Jeremy Stanley <98883b97e35b7bb1ac282bb863f2e9d917db0454@yuggoth.org>
Reviewed-by: Jeremy Stanley <98883b97e35b7bb1ac282bb863f2e9d917db0454@yuggoth.org>
Tested-by: Jenkins

redhat-openstack/pbr,redhat-openstack/pbr,openstack-dev/pbr,openstack-dev/pbr,citrix-openstack-build/pbr,citrix-openstack-build/pbr,WiFast/pbr,varunarya10/pbr,openstack-dev/pbr,WiFast/pbr,JioCloud/pbr,klmitch/pbr,JioCloud/pbr,varunarya10/pbr,citrix-openstack-build/pbr,klmitch/pbr