The combined fixes for the two related bugs resolve the problem where
SIGHUP breaks the nova-compute service. Bump the minimum requirements
for oslo.privsep and oslo.service to make sure these fixes are in place,
and add a reno to advertise resolution of the issue.
This also bumps oslo.utils to match the lower constraint from
oslo.service.
Change-Id: I39ead744b21a4423352a88573f327273e4d09630
Related-Bug: #1794708
Related-Bug: #1715374