Network Manager - OpenVPN - Zombie Processes After Disconnection

[João Mateus Paiva Dalvi]

Problem happens on 18.04, fresh install, updated to the latest packages.
Package is network-manager-openvpn version 1.8.2
OpenVPN Network Manager applet keeps zombie openvpn processes after disconnection or connection loss. This odd behavior makes user experience unstable, needing manual "kill -9" of dozens of processes or system reboot, as these processes keep trying to claim tun0 and establish connections again, sometimes making new connections attempts impossible.
This problem is errant, and hard to replicate exactly the same way again. Sometimes you see plenty of zombie processes writing to /var/log/syslog, sometimes not.
This problem is already solved upstream (version 1.8.3+ it seems), so a backport of network-manager-openvpn from cosmic, wich has its 1.8.4 version, should solve the problem.