cannot process notifications with list payload

[gordon chung]

when building a sample from notifications, if the payload is a list, errors are thrown because we expect payloads to be dict.

https://github.com/openstack/ceilometer/blob/master/ceilometer/sample.py#L83-L98

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/213202

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/213202
Committed: https://git.openstack.org/cgit/openstack/ceilometer/commit/?id=c17b294aa9d7820d83cda4e25c7e36d01f1651aa
Submitter: Jenkins
Branch: master

commit c17b294aa9d7820d83cda4e25c7e36d01f1651aa
Author: gordon chung <email address hidden>
Date: Fri Aug 14 11:28:54 2015 -0400

    handle list payloads in notifications

    when processing notifications, the assumption is the payload is
    always a dict. the odd cases, it's not. we should ignore these
    cases.

    Change-Id: I8e24d0c0ba42a67f2877051c683358a411f19e48
    Closes-Bug: #1484972