Dockerfile: move back to ubuntu:16.04 (needed for the required clang version)
Dockerfile: move back to ubuntu:16.04 (needed for the required clang version)

versatica/mediasoup,ibc/MediaSoup,versatica/mediasoup,versatica/mediasoup,versatica/mediasoup,ibc/MediaSoup,versatica/mediasoup,versatica/mediasoup,versatica/mediasoup,versatica/mediasoup,versatica/mediasoup,ibc/MediaSoup