Fix incorrect ca argument for heat ceilometer client

Currently Heat ceilometer client are passing the wrong ca argument
during client instantiation. It will cause heat fail to connect to ceilometer
if it's configured with SSL.

https://github.com/openstack/python-ceilometerclient/blob/master/ceilometerclient/v2/client.py#L53

Closes-bug: #1391792

Change-Id: Ib32dfede0ece78bc39e0cab213cb51df8eb62eb6
Merge "Fix incorrect ca argument for heat ceilometer client"