Openshift overrides the `service` label for
all metrics in the cluster. Update the label
from `service` to `subsystem` for the status
metrics query. This helps us differentiate
between requests from composer and the worker
server.
Add a helper function to register the same metrics
for both the worker and composer - the only difference
being the subsystem name. The function checks if the
metric has already been registered and, if so, returns
the already registered metric.