Revert "Support mirror registries with path component (#1707)"

[tejal29]

Fixes #1793 #1790 #1791

[stevemk14ebr]

Is there a fix for this planned? I expected to be able to take an existing dockerfile such as:

FROM golang:1.17-alpine

And instruct kaniko to use my mirror like this (fake domain names here for the example):

--registry-mirror harbor-ci.internal.io/team-images/library

Which would then pull from this final URL as if it was my FROM line:

harbor-ci.internal.io/team-images/library/golang:1.17-alpine

however, in reality this fails with the error:

error building image: registries must be valid RFC 3986 URI authorities:

I believe this occurs because of the URI /team-images/library/, but that is required to be passed keep dockerfiles independent from the build environment they're executed in, while pulling from the correct place on the mirror.

if it's unreasonable to fix --registry-mirror, then perhaps a new commandline option. Maybe --mirror-prefix or something.