builder: Drop dead code in gvir_sandbox_builder_clean_post_stop
builder: Drop dead code in gvir_sandbox_builder_clean_post_stop

At the 'cleanup' label we try to unref @child. However, whenever
the label is entered there's no chance for the variable to be
anything else than NULL rendering those two lines as dead code.
Drop it. And it's the same story with @info.

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

agx/libvirt-sandbox-debian,agx/libvirt-sandbox-debian,libvirt/libvirt-sandbox,libvirt/libvirt-sandbox,agx/libvirt-sandbox-debian,libvirt/libvirt-sandbox,agx/libvirt-sandbox-debian,agx/libvirt-sandbox-debian