db2 does not allow None as a key for user_id in user collection

[Tong Li]

mongodb allows None value as a key for _id field, but db2 does not.
in many of the openstack glance meters, the user_id was hard coded as None.
This causes problem for DB2 as the None value is not allowed for key field.
this patch will fix the problem when meters coming with user_id
being set to None.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/49095
Committed: http://github.com/openstack/ceilometer/commit/77a0603bebcb25fba94ddfb40e50baed46eb9384
Submitter: Jenkins
Branch: master

commit 77a0603bebcb25fba94ddfb40e50baed46eb9384
Author: Tong Li <email address hidden>
Date: Wed Oct 2 09:18:14 2013 -0400

    db2 does not allow None as a key for user_id in user collection

    mongodb allows None value as a key for _id field, but db2 does not.
    this patch will fix the problem when meters coming with user_id
    being set to None.

    Change-Id: If48e5117198f3e9ad834e4f7fa58ec27c57a8bc8
    fixes: bug #1234165

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/49499

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: milestone-proposed
Review: https://review.openstack.org/49507

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/49507
Committed: http://github.com/openstack/ceilometer/commit/cfd59acb1f6b5734669a31733e95a86a89e73abf
Submitter: Jenkins
Branch: milestone-proposed

commit cfd59acb1f6b5734669a31733e95a86a89e73abf
Author: Tong Li <email address hidden>
Date: Wed Oct 2 09:18:14 2013 -0400

    db2 does not allow None as a key for user_id in user collection

    mongodb allows None value as a key for _id field, but db2 does not.
    this patch will fix the problem when meters coming with user_id
    being set to None.

    fixes: bug #1234165
    (cherry picked from commit 77a0603bebcb25fba94ddfb40e50baed46eb9384)

    Change-Id: Icdb53e0835faf7d469a8af882a3dcd7e161a1d1d