legacy-mgcp: Add jitter buffer on the uplink receiver

Default usage values are defined in mgcp node, and can be per-BSC
overriden on each bsc node

This commit is a forward-port of openbsc.git Change-Id
Ibf3932adc07442fb5e9c7a06404853f9d0a20959.

Change-Id: Ie19a64ac09f9d51f2434ad0d7925610fc919a90e
5 files changed