vivian: make local registry container persistent between builds unless clean needed.

With current implementation, the local registry is removed/cleaned when the its container is stopped or the host machine reboot. This cause 'make vivian' fail to start the gateway unless calling make gateway-container again which is unnecessary.

The changes is to make the local registry persist and keep its previously pushed images. It will try to (re)start the existing one instead of creating a new one. If need be, the local registry can be removed with make clean. The container name also be changed to a less generic one. This is to avoid the case when the host already has a container named 'registry'.