Log Message:
Update to dhcpcd-5.1.5 with the following changes:
* arc4random from OpenBSD imported for better randomness on Linux
* -h, --xidhwaddr uses the last 4 bytes of the hardware address as
  the DHCP xid
* no longer warn about InfiniBand being an unsupported family
* infinite lease times are valid when reading old leases
* discard address correctly if lease is invalid