Disable of KPI group associated with Interval PM ME should disable PM

The KPI shared library allows for groups of metrics to be enabled or disabled.  Currently OpenOMCI always creates the interval PM counters that monitor a specific OMCI entity (bridge port, UNI, ANI, ...) when that ME is also created.

The creation of the PM Interval MEs should take into account the status of the PKI group.  Currently the interval data is collected and sent to the PKI library for publishing, where its enable/disable state is examined.

This is probably low priority since the outward behavior for a disabled PM Interval works as expected (no message on the voltha.kpi topic). Adding this may help conserve some CPU resources once we begin to scale up the number of ONUs on a PON.