MetricsFilter unaware of uri template variables, causes memory issues

[twicksell]

MetricsFilter is unaware of uri template variables. The end result of this is a large pile of un-grouped metrics which aren't terribly useful. Given a high enough volume this can also cause a memory issue pretty quickly.

Example data:

"counter.status.0.v1.customer.216352347804695987.subscription.Streaming.cancelPredictionResponse": 4,
"counter.status.0.v1.customer.216352546813607503.subscription.Streaming": 2,
"counter.status.0.v1.customer.216352546813607503.subscription.Streaming.cancelPredictionResponse": 1,
"counter.status.0.v1.customer.216352546813614321.subscription.Streaming": 7,
"counter.status.0.v1.customer.216352546813614321.subscription.Streaming.cancelPredictionResponse": 7,
"counter.status.0.v1.customer.216352546813635000.subscription.Streaming": 5,
"counter.status.0.v1.customer.216352546813635000.subscription.Streaming.cancelPredictionResponse": 5,
"counter.status.0.v1.customer.216352546813647633.subscription.Streaming": 3,
"counter.status.0.v1.customer.216352546813647633.subscription.Streaming.cancelPredictionResponse": 3,
"counter.status.0.v1.customer.216352546813969969.subscription.Streaming": 1,

Would expect the actual id's to be replaced by the path variable "customerId"