allocate_fixed_ip should cleanup with correct param

[jichenjc]

in nova-network , when allocate_fixed_ip failed for some unknown reason

it will add
cleanup.append(fip.disassociate)

to cleanup the stuffs it did when handle exception
but the function is following in objects/fixed_ips.py
def disassociate(self, context):

so the cleanup function will not be executed correctly

try:
                        f()
                    except Exception:
                        LOG.warn(_('Error cleaning up fixed ip allocation. '
                                   'Manual cleanup may be required.'),
                                 exc_info=True)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/110598

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/110598
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=4dcfa79058a407eb7a6ce83f4d804df19ec95026
Submitter: Jenkins
Branch: master

commit 4dcfa79058a407eb7a6ce83f4d804df19ec95026
Author: jichenjc <email address hidden>
Date: Mon Jul 21 07:53:07 2014 +0800

    Add context as param to cleanup function

    In nova-network, when we start
    to cleanup the stuffs it did when handle exception
    but the function is following in objects/fixed_ips.py
    def disassociate(self, context):
    so the context param is lost and it can lead to problem.

    Change-Id: I66a1681f47fc69bf0fd92137ee27481659833bef
    Closes-Bug: #1350268