Incorrect openstack credential tenant name

[Ian Booth]

Juju incorrectly enforces that the tenant name credential attribute for openstack clouds is mandatory. And it uses the underlying goose cred parsing to incorrectly set tenant id to tenant name, see https://github.com/go-goose/goose/issues/67

The assumption that tenant name is mandatory is used when printing errors etc. So some rework is required to make this optional, after the goose fix lands. See various methods in github.com/juju/juju/provider/openstack/credentials.go

[Heather Lanigan (hmlanigan)]

id and name are usually interchangeable with openstack commands, but not in filters to my knowledge.

Tenant is required for v2 authentication. Project is required for scoped authorization in v3, not for unscoped authorization which juju uses.

[Heather Lanigan (hmlanigan)]

The id/name comment in #1 is not true for v3 authentication:
https://developer.openstack.org/api-ref/identity/v3/#authentication-and-token-management

[Heather Lanigan (hmlanigan)]

The openstack environment variables have less granularity between id/name than the openstack config yaml files:
https://docs.openstack.org/python-openstackclient/pike/cli/man/openstack.html

[Vinodhini (vinu-b)]

PR committed : https://github.com/go-goose/goose/pull/72