Add database users for instances.

Create, List, and Delete operations are supported. Because the
password is write-on-create only and otherwise omitted, this property
is fully implemented. Create is reimplemented to format as a list,
expected by the service.

Change-Id: Id8b09ea7863d402ccda5b33ad947cd54344cf85b
Fix find for resources with id_attribute

The find method had 'id' hard coded rather than using id_attribute.
The error message printed by find was not correct for resources that
do not have a resource_name, so I added the get_resource_name()
method.

Change-Id: I53965e74bd29081f3c3fa3f1da406aeb71cc2c01
Floating ip does not have an id

1) Floating ip does not have an id, it uses floating_ip_address
   as the key.
2) There is no attribute that is similar to a name.
3) Set resource_name for person friendly print.

Change-Id: I9e0d21dcf446ad19fe416a868e3ddfa804b99f36
Add support for telemetry sample Statistics

List operation only with optional query string filters.
Statistics endpoint requires a meter name in forming the URL.

Change-Id: I3bf0e051783b9fa601b2aaaa940dbac0bc93d69c
Merge "Add database users for instances."
Merge "Fix find for resources with id_attribute"
Determines version from auth_url when not explicit

This changes the default version to None instead
of '3', and grabs the version from the auth_url.
Before, passing it only a v2 auth_url would break
with no good explanation.

Change-Id: I97b22ee9b978c34e98c220441fbea940b76e8e5f
Co-Authored-By: Telles Mota Vidal Nóbrega <tellesmvn@lsd.ufcg.edu.br>
Closes-Bug: 1357109
Merge "Determines version from auth_url when not explicit"
Merge "Add support for telemetry sample Statistics"
Prepare for auth plugins

In order to get ready for auth plugins I kind of needed to
turn auth plugins on their head.  The goals:

* The plugin should know what to construct based on what the
  user provides.  If a token is provided, use it.
* If a token is provided and it expires, allow the user to reauth
  with user name and password without the user having to do
  anything special.
* Support auth plugin names like identity_v2 and identity_v3 where
  the user does not need to know exactly what method they are
  using.
* Keep is simple.

In the simple department, I think this makes it simplier for the
user.

Change-Id: I7778438930bad2a32f79189b46d4fe7dbfbb67f6
Use stevedore to load authorization plugins

Add basic infrastructure to load authorization plugins with
stevedore.

Change-Id: I4828be6537bbe865b43ec43de41f6060ea8f2c98
Make user_id a higher priority for v2 auth

Change-Id: I766440d5f8bd60b685f30254acb3987cabd161f0