dnsmasq fails to start on ubuntu 18.04 based image

[Damian Dąbrowski]

**Bug Report**

What happened: when running ubuntu based bifrost_deploy image, dnsmasq systemd service fails to start until I comment out 'PIDFile=/run/dnsmasq/dnsmasq.pid' line in /etc/systemd/system/multi-user.target.wants/dnsmasq.service

# journalctl -u dnsmasq
-- Logs begin at Mon 2020-01-13 16:24:18 UTC, end at Mon 2020-01-13 16:36:11 UTC. --
Jan 13 16:31:51 seed systemd[1]: Starting dnsmasq - A lightweight DHCP and caching DNS server...
Jan 13 16:31:51 seed dnsmasq[3955]: dnsmasq: syntax check OK.
Jan 13 16:31:53 seed systemd[1]: dnsmasq.service: New main PID 3967 does not belong to service, and PID file is not owned by root. Refusing.
Jan 13 16:31:54 seed systemd[1]: dnsmasq.service: New main PID 3967 does not belong to service, and PID file is not owned by root. Refusing.
Jan 13 16:31:54 seed systemd[1]: dnsmasq.service: New main PID 3967 does not belong to service, and PID file is not owned by root. Refusing.
Jan 13 16:33:24 seed systemd[1]: dnsmasq.service: Start-post operation timed out. Stopping.
Jan 13 16:33:24 seed systemd[1]: dnsmasq.service: Failed with result 'timeout'.
Jan 13 16:33:24 seed systemd[1]: Failed to start dnsmasq - A lightweight DHCP and caching DNS server.