Description of problem:
-----------------------------------------
A running process may refer to a renamed executable
referenced by /proc/$pid/exe, which happens with
updated executables on RPM based systems.
In that case we defer to the path in /proc/$pid/cmdline
if it exists.

Cisco is reporting after upgrading rpms they have to clean up stale pids around the neutron dhcp agent service and requesting a backport upstream python-oslo-rootwrap fix to OSP-5 (Icehouse) which was fixed in python-oslo-rootwrap 2.3.0 currently we ship in OSP-8 (Liberty), see additional details for the specific upstream merged commit. 
 

Version-Release number of selected component (if applicable):
-----------------------------------------
python-oslo-rootwrap-1.0.0-2

How reproducible:
-----------------------------------------
100% in customers environment

Steps to Reproduce:
-----------------------------------------
1. Update an rpm.

2. A running process refers to a renamed executable referenced by /proc/$pid/exe triggering the KillFilter error.

3. The neutron-dhcp-agent.service's pids are in a stale state requiring clean up. 

Actual results:
-----------------------------------------
The customer reports after upgrading rpms they have to clean up stale pids around the neutron dhcp agent service.

Expected results:
------------------------------------------
Oslo Rootwrap should in the case of an rpm upgrade defer to the path in /proc/$pid/cmdline if it exists. 


Additional info:
-----------------------------------------
Upstream merged commit for liberty:


Handle renamed executables with KillFilter
-----------------------------------------
https://review.openstack.org/#/c/210541/3