Set WorkingDir to empty, not / for conformance
Set WorkingDir to empty, not / for conformance

Signed-off-by: TomSweeneyRedHat <tsweeney@redhat.com>

Closes: #1098
Approved by: rhatdan

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