Fix tarball publisher ctx handling (#545)
Fix tarball publisher ctx handling (#545)

Previously, we'd use the ctx from the Build invocation, but because
remote stashes the remote.WithContext option, when we later go to fetch
the actual base image to write it out to a tarball, it will fail because
the Build ctx was cancelled.

For whatever reason, NewGo takes a ctx, so this change propagates the
badness from remote so we can use the NewGo ctx when we fetch base
images.
ko-build/ko,ko-build/ko