R1:a424fec7bb3e

Aphlict - fix getActiveListenerCount return value

Summary: Ref T7126. Dictionaries do not have a `length` property unlike arrays resulting in the `getActiveListenerCount()` function returning undefined results. Using the `length` property on the array of keys will work.

Test Plan: Using `wscat` to generate multiple connections to the server, establish new ones and close others while keeping an eye on the displayed `clients.active` value.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley…