rofiles: Fix --copyup when creating a new file

rofiles: Fix --copyup when creating a new file

This tripped up the `docbook-dtds` `%post` in my experiments
with doing rpm-ostree for buildroots.

I cloned and built [xfstests](https://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git)
but haven't yet investigated actually running it.

In the meantime let's do the obvious fix here; we need to distinguish
between "copyup enabled" and "actually did a copyup" in the open path
at least, since if we didn't do a copyup we don't need to re-open.

Closes: #1396
Approved by: jlebon