Fix setting of users default tenant

Keystone v2.0 api expects tenantId to define the default
tenant, not tenant_id (which is the EC2 credential tenant)
Always pass email property

Otherwise the property is missing in the created
user, which causes compatibility issues later (for example
bnc#859463)
Merge pull request #163 from dirkmueller/release/roxy/master

Fix setting of users default tenant