Improve swift's keystoneauth ACL support

Below three bug reports talk about one thing.
Current keystoneauth ACL supports as:

tenant_name:user_id         ok
tenant_name:user_name       no
tenant_name:*               no
tenant_id:user_id           ok
tenant_id:user_name         no
tenant_id:*                 no
*:user_id                   ok
*:user_name                 no
*:*                         no

This patch will make all of above work fine.
Applying (tenant/user)name could let user put or get their data in a
more readable way. The tenant_name:* and *:user_name is suitable for
many usage.

note: to keep compatibility here add a new keystone.identity just for
authorize() itself and leave env['keystone.identity'] to other
middlerwares.

Fixes: bug #1020709
Fixes: bug #1075362
Fixes: bug #1155389
Change-Id: I9354dedaad875117f6a9072c67e9ecf69bfca77e
Merge "Improve swift's keystoneauth ACL support"