main/dhcpcd: 10.0.4 gets IPs, but fails to background itself

While testing an Alpine edge AWS Tiny-Cloud image, I noticed that although dhcpcd (10.0.4) successfully picked up IPs from DHCP, it failed to background itself.

 * Starting networking ... *   lo ... [ ok ]
 *   eth0 ...dhcpcd-10.0.4 starting
DUID 00:01:00:01:2c:d2:c9:cf:0a:15:c6:f6:91:91
eth0: IAID c6:f6:91:91
eth0: soliciting an IPv6 router
eth0: Router Advertisement from fe80::8e7:ddff:fe5c:ad3b
eth0: no global addresses for default route
eth0: adding route to 2600:1f14:2a4a:8902::/64
eth0: soliciting a DHCPv6 lease
eth0: soliciting a DHCP lease
eth0: offered 172.30.2.109 from 172.30.2.1
eth0: probing address 172.30.2.109/24
eth0: ADV 2600:1f14:2a4a:8902:55b4:ea04:18cf:3342/128 from fe80::8e7:ddff:fe5c:ad3b
eth0: REPLY6 received from fe80::8e7:ddff:fe5c:ad3b
eth0: adding address 2600:1f14:2a4a:8902:55b4:ea04:18cf:3342/128
eth0: renew in 70, rebind in 112, expire in 450 seconds
eth0: adding default route via fe80::8e7:ddff:fe5c:ad3b
forked to background, child pid 1870
dhcpcd_fork_cb: truncated read 0 (expected 4)
ifup: failed to change interface eth0 state to 'up'
 [ !! ]

Building a new AWS image that uses dhcpcd-10.0.2-r1 from the main 3.18 repo solves this issue.

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