Fix error reporting when parsing trans+image
Fix error reporting when parsing trans+image

Use the right variable to make sure transport and image are
colon-separated in error reports.

Changes user-visible strings.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

Closes: #1361
Approved by: rhatdan

projectatomic/buildah,rhatdan/buildah,nalind/buildah,rhatdan/buildah,nalind/buildah,rhatdan/buildah,nalind/buildah-1,nalind/buildah-1,TomSweeneyRedHat/buildah,nalind/buildah-1,TomSweeneyRedHat/buildah,projectatomic/buildah,projectatomic/buildah,TomSweeneyRedHat/buildah