This reverts commit 05f20a5396b8a1f463129b99bbe23b8b7862afdd.
Apparently skopeo is properly cloud native too and doesn't support ipv6
either. I think it is pulling the same docker
distribution/reference/regexp.go lib in and using docker's regex.
The error we get from skopeo:
time="2019-04-10T15:15:48Z" level=fatal msg="Invalid source name docker://[2607:ff68:100:54:f816:3eff:fef2:fc69]:5000/zuul/nodepool:latest: invalid reference format"
Change-Id: I6f916574c9f46e8fdd2464465e2b36ecf8719b16
ba4b2c68b9