Remove libvirt-python from upper-constraints

... when installed from distribution.

This is mostly to fix Ironic's gate as their ecosystem is too
broad and complex to quickly remove libvirt-python from all
possible requirements.txt

More details inline.

See also: https://review.opendev.org/c/openstack/devstack/+/798514
aka f0bf2bdff12b66eefbb2eae83e919611eb7cc76d

Change-Id: Ic44daf15e952bbe3c424984ffb2474261e68008f
1 file changed