allow to specify assignment driver

this is needed for read-only-ldap as per
http://adam.younglogic.com/2013/10/read-only-ldap-in-keystone/
which replaces hybrid auth
Merge pull request #160 from SUSE-Cloud/readonlyldapsupport

Add support for read-only-ldap
Add migration script for assignment driver

Also made this attribute required, to simplify things.
Merge pull request #161 from vuntz/assignment-driver

Add migration script for assignment driver
Do not fail immediately if wakeup fails, retry instead

Since we restart keystone immediately and then do a wakeup call,
sometimes the wakeup call fails because it cannot connect to the server
yet.

To avoid that, we should just retry the wakeup.

https://bugzilla.novell.com/show_bug.cgi?id=859678
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)
Use provider for setting token format

The other setting triggers a deprecation warning.
Merge pull request #162 from vuntz/retry-wakeup

Do not fail immediately if wakeup fails, retry instead
Merge pull request #164 from dirkmueller/pki_token

Use provider for setting token format
Merge pull request #163 from dirkmueller/release/roxy/master

Fix setting of users default tenant