Allow dispersion tools to use keystone server with insecure certificate

The swift-dispersion-populate and swift-dispersion-report tools now
accept a --insecure option.

Also, dispersion.conf now has a keystone_api_insecure option.

Default is obviously to use the secure path.

DocImpact

Change-Id: I4000352e547d9ce5b08ade54e0c886281caff891
Merge "Allow dispersion tools to use keystone server with insecure certificate"