Cinder API allows specifying tenant_id to get tenant
specific resource usage. This was missing in the client.
This fix should allow fetching tenant specific resource usage
directly from the client. Added tenant argument to the limits CLI.

Closes-Bug: #1580562
Change-Id: I3fbd6341f6d018a79e7c343107ac974b6fbb9239

Added request_ids attribute to resource object for all the
cgsnapshots, consistencygroups, qos_specs, quota_classes,
quotas and services APIs by updating following APIs:

cgsnapshots: delete, update
consistencygroups: delete, update, create
qos_specs: delete, associate, disassociate, disassociate_all
quota_classes: update
quotas: update
services: enable, disable, disable_log_reason

These changes are required to return 'request_id' from client to
log request_id mappings of cross projects.

For more details on how request_id will be returned to the caller,
please refer to the approved blueprint [1] discussed with the
cross-project team.
[1] http://specs.openstack.org/openstack/openstack-specs/specs/return-request-id.html

DocImpact
'request-ids' will be returned as an attribute with response object.
User can access it using 'res.request_ids' where 'res' is a
response object.

Change-Id: I7b399512fcec9ecd31938656deb60e325bb76ad4
Partial-Implements: blueprint return-request-id-to-caller

This is the first step of moving functional testing
into the project tree.  This change just moves
all of the unit tests to be under a dedicated tests/unit
directory.

Follow up patches will add the functional directory and
start moving tempest CLI tests there.

Change-Id: I9dc0b8f761676c1b3bbdeb03e2f44b35f75c693e