Fix serialization of iterable types
Fix serialization of iterable types

So far, we have not supported serialization of iterable type
arguments to RPC methods. However, the recent change to pass
args as a tuple instead of forcing everything to kwargs means
that serialization of non-keyword args is broken. This patch
adds that support, as well as tests for the serializer, which
should have been there in the first place.

Related to blueprint unified-object-model

Change-Id: Ie02fffd89d9b79b4bc8270c14b2860c0e37d7a92

openstack/oslo.versionedobjects,citrix-openstack-build/oslo.versionedobjects