nova-api: remove unuseful expect error in v2.1 service delete method

[Eli Qiao]

in nova/api/openstack/compute/plugins/v3/services.py
we found :
    @extensions.expected_errors((400, 404))
     def delete(self, req, id):

by checking code, there isn't any badrequest exception raising,
we need to remove 400 from expected code.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/180827

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/180827
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=bcb9769356bac6e9da7aa81b92affd61f9963c8c
Submitter: Jenkins
Branch: master

commit bcb9769356bac6e9da7aa81b92affd61f9963c8c
Author: Eli Qiao <email address hidden>
Date: Thu May 7 09:51:30 2015 +0800

    API: remove unuseful expected error code from v2.1 service delete api

    There isn't any BadRequest exception raise from this api method.
    Remove it.

    DOCImpact: service delete will not raise 400.
    Closes-Bug: #1452522

    Change-Id: Iad489926176aa5ebf4ab914f1ba6e4546e913fc5