Remove SCREEN_LOGDIR from devstack
Remove SCREEN_LOGDIR from devstack

SCREEN_LOGDIR has already been deprecated [1]
[1] https://review.openstack.org/#/c/499186

Change-Id: I7b87a52b8d573d384e8c30b5122122609d60a1fc

openstack/ironic-inspector,openstack/ironic-inspector