message: updating Dockerfile.rocm to pick a specific version of the rocm libraries (v 2.6 for now) instead of always picking the latest.
diff: FROM ubuntu:xenial
  MAINTAINER Jeff Poznanovic <jeffrey.poznanovic@amd.com>
  -ARG DEB_ROCM_REPO=http://repo.radeon.com/rocm/apt/debian/
  +ARG DEB_ROCM_REPO=http://repo.radeon.com/rocm/apt/2.6/
  ARG ROCM_PATH=/opt/rocm
  ENV DEBIAN_FRONTEND noninteractive
  