Fix metering service endpoint path

After installing ceilometer with the metering cookbook, invoking the
ceilometer CLI fails because the API base URL used is
http://127.0.0.1:8777/v1/v2 which means that the base endpoint path of
/v1 is incorrect and it should be simply /.

Change-Id: Id65a17a888175c7b2fe2d3171147cedb66921cc9
Partial-Bug: #1277742
Merge "Fix metering service endpoint path"