Close the listen sockets in child processes

By keeping the listen sockets open, the children were preventing the
daemon from being restarted cleanly. Once the child has forked these
listen sockets are no longer needed by that process, so can be closed.
Ignore EINTR errors from main poll() loop

When trying to connect the strace tool to the daemon's main process, the
daemon would die because strace interrupted the poll() causing it to
return EINTR.

It should be safe to ignore EINTR errors from poll in this case. Either
the received signal will be otherwise ignored by the process, or it will
cause it to terminate.