Object hash test fails to detect changes when serialize_args is used

[Dan Smith]

The object hash test will fail to detect method signature changes when something like the serialize_args decorator is used. The test needs to drill down until it finds the remotable level and do the calculation there.

[Dan Smith (danms)]

This was fixed in:

commit 767c5d65b625a224f818bf5f8b5ac8cd0a35d7e2
Author: Mikhail Durnosvistov <email address hidden>
Date: Mon Aug 11 16:52:10 2014 +0300

    Move and generalize decorator serialize_args to nova.objects.base

    It would be nice use decorator `serialize_args` as general-use
    decorator. Note that this single-purpose decorator was covering
    up our ability to drill down to the actual method implementation
    for hash calculation in the TestObjectVersions test. This patch
    also enhances the decorator to be transparent, and makes the
    test able to drill down through multiple layers of decorators
    to find the actual implementation.

    Co-Authored-By: Dan Smith <email address hidden>
    Change-Id: Ie454bffba113d7b3a863e975b2fb0ee6fb1dd552