Run telemetry in javelin if resources.yaml says so

In previous code telemetry checks were always run (if there
were servers to check). If the environment did not have ceilometer
services this would fail.

check_telemetry now checks that there is a true value on the
'telemetry' key in resources.yaml. No configuration is required for
the telemetry checks, so only a key with a value is required.

Change-Id: I84e0f5938ec808537043dba29a896f991779b04c
Merge "Run telemetry in javelin if resources.yaml says so"