pkg/init: Do not run inits in the background

We want them to run in sequence. For example we want mounts to be done (done by
`pkg/runc/etc/init.d/010-onboot`) before we start services (done by
`pkg/containerd/etc/init.d/020-containerd`). This was most likely introduced by
28b4245b12 ("Move onboot startup script to runc package").

None of the initscripts in pkg/* block, but some in projects (selinux and
logging, not updated here) do.

Signed-off-by: Ian Campbell <ijc@docker.com>

pkg/init/bin/rc.init

@@ -122,5 +122,5 @@ ulimit -p unlimited
 INITS="$(find /etc/init.d -type f | sort)"
 for f in $INITS
 do
-	$f &
+	$f
 done