This tag controls the version of the Dockerfile used for building the container.
The TRex version is controlled by the TREX_VER variable in Dockerfile (e.g. ENV TREX_VER "v2.56").
-TRex is installed in container from https://trex-tgn.cisco.com/trex/release/
+TRex is installed in container from https://github.com/cisco-system-traffic-generator/trex-core/releases
The Test VM version is controlled by the VM_IMAGE_VER variable in Dockerfile (e.g. ENV VM_IMAGE_VER "0.8").
The VM is extracted from google storage (http://artifacts.opnfv.org)