libguestfs: Makes libguestfs more verbose and repairs __slots__.

Signed-off-by: Jiří Župka <jzupka@redhat.com>
virt: libguestfs repair problem in test virt-edit

Repairs is need due to change in utils_libguestfs.py.

Signed-off-by: Jiří Župka <jzupka@redhat.com>