Fixes T84 with D3190. This isolates NM to not use the system-wide
dnsmasq.conf and sets the dhcp-leasefile to NetworkManager's
NMSTATEDIR where it belongs in this instance.
Patch provided here has also been submitted and accepted upstream.
Side note: Though 1.12.0 should be binary compatible with previous
versions, Steam stopped working when testing 1.12.0, so I've kept
this back to 1.10.x series for the time being.