This adds new functional tests, which are supposed to be run
on devstack with a running instance of prometheus.
It tests all of the cli commands as well as all the functions
exposed in the python client.
These tests could be included into the telemetry-dsvm-integration
jobs in the future to use the same devstack vm.
Change-Id: Ibd6deec559465bf3cb7480681b816f55bdf9010e
e8961fdf62