(I had a disk image containing unmodifiable binary software that would
overwrite dhcpcd's sane copy of /etc/resolv.conf, at a nondeterministic
point in time, with something completely bogus.  That screwed up
startcmdstatus reports; this helps out with that case (in combination
with other custom scripting that returns /etc/resolv.conf to sanity).

Note though that we only retry infinitely once runstartup has
successfully gone to the background; up til then, we're limited to about
a minute's worth of retries.  Likewise, we don't retry forever if
runstartup itself experiences an error.  We only retry forever if we
actually have a status to send.