Remove outdated docstring for XenApi driver's options

XenAPI's driver options's help strings can explain how to
use these options, so remove these duplicated and outdated
docstring.

Change-Id: I3de257e75ba13352e9460070f5bb2a6d7cf36a4e
Use wsgi.response for v2.1 API

Now a decorator @wsgi.response() can be used for specifying success
status code. Most v2.1 APIs use the decorator and it makes the code
more readable. This patch replaces webob.Response with the decorator
for the other APIs.
In addition, this patch changes some orders of decorators for showing
success code and expected error codes clearly.

Even if applying this patch, some webob.Response() calls still exist
under the path nova/api/openstack/compute/plugins/v3/ because these
cases need to contain some information in a response header.

Partially implements blueprint v2-on-v3-api

Change-Id: I419819b8e55427979e8d82b972cd237952a5b06b
Use common get_instance call in API plugins

Cleanup API to use common get_instance call which
automatically does exception handling. Not all cases
are handled in this patch as some require more
significant testcase rework and are done in future
patches to make it easier to review.

Change-Id: Id27350e6562636f81347b490db649744b6b41186
Split out num instances filter unit tests

Break out the unit tests for num instances filters from
test_host_filters.py into its own file. In the process, we mock out the
database calls for getting aggregate information instead of creating
database records.

Change-Id: I71516cee8b1660e8e8f76eae4ae831b34232289e
remove use of explicit lockutils invocation in tests

Instead of passing lockutils loading explicitly in the test run
command line, provide the support for individual test classes to ask
that lock_path is setup with the REQUIRES_LOCKING = True class
parameter.

Augment all classes that currently fail without this with
REQUIRES_LOCKING = True. Hopefully many of those can be individually
removed in the future so we can get out of needing external locking in
any of our unit tests.

Change-Id: I56229e93ad61ac823646a4119a035d36c3400173
Update docstring for check_instance_shared_storage_local

The check_instance_shared_storage_local method is getting
a nova instance object so update the docstring to reflect
that.

Part of blueprint kilo-objects

Change-Id: I2fe671f47bc73e5bf292abce7ba678e1cf59e6d9
Merge "Use wsgi.response for v2.1 API"
Merge "Use common get_instance call in API plugins"
Merge "remove use of explicit lockutils invocation in tests"
Merge "Update docstring for check_instance_shared_storage_local"
Merge "Remove outdated docstring for XenApi driver's options"
Merge "Split out num instances filter unit tests"