trust authentication

This patch enables authenticating by using a trust. The trust ID
must be set with the parameter --os-trust-id or the env variable
OS_TRUST_ID. Trusts are available for the identity v3 API.

Co-Authored-By: Florent Flament <florent.flament@cloudwatt.com>
Change-Id: Iacc389b203bbadda53ca31a7f5a9b8b6e1a1f522
Merge "trust authentication"
Remove keyring support from openstackclient

* The encryption it purports to offer is completely insecure.
* It also appears to be broken.

Closes-Bug: #1319381
Change-Id: Id15ecfbbfd15f142b14c125bfd85afd5032699ac
Merge "Remove keyring support from openstackclient"