tremplin: set lxdbr0 DHCPv4 expiry to infinite We would like containers to maintain their IP addresses for at least as long as the container is running. Set the DHCP expiry to infinite to avoid the hourly lease renewals which may cause an IP address reassignment. BUG=chromium:938792 TEST=networking.service logs in container show no expiry for IP Change-Id: Ibd8f4b86e7c48aa60e098b22662ea65457e77b27 Reviewed-on: https://chromium-review.googlesource.com/1740676 Tested-by: Stephen Barber <[email protected]> Commit-Ready: ChromeOS CL Exonerator Bot <[email protected]> Legacy-Commit-Queue: Commit Bot <[email protected]> Reviewed-by: Joel Hockey <[email protected]>