Connection Limit filter reporting 18 quintillion active connections

We have observed that Envoy with the Connection Limit Filter configured, at some point will report 2**64 active connections for the metric `envoy.connection_limit..active_connections`.

This seems suspicious and could be indicative of some integer overflow.

This did not result in a crash, but did result in some connections being limited when it was not intended.

We configured the filter with a `max_connections` of 56000 and `delay` of 500ms