compose tree: Cleanup workdir always
compose tree: Cleanup workdir always

Particularly if we hit the cached case, but we might as well always do
it.

mdshuai/rpm-ostree,mdshuai/rpm-ostree,giuseppe/rpm-ostree,mdshuai/rpm-ostree,cgwalters/rpm-ostree-cgwalters,tmp-user/rpm-ostree,tmp-user/rpm-ostree,cgwalters/rpm-ostree-cgwalters,giuseppe/rpm-ostree,tmp-user/rpm-ostree,cgwalters/rpm-ostree-cgwalters,mdshuai/rpm-ostree,giuseppe/rpm-ostree,tmp-user/rpm-ostree,giuseppe/rpm-ostree