start_stop_daemon: NOMMU fix; smaller fixes

diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c
index ea7b475..f7c6209 100644
--- a/libbb/vfork_daemon_rexec.c
+++ b/libbb/vfork_daemon_rexec.c
@@ -244,8 +244,6 @@
 {
 	int fd;
 
-	fd = xopen(bb_dev_null, O_RDWR);
-
 	if (flags & DAEMON_CHDIR_ROOT)
 		xchdir("/");
 
@@ -255,6 +253,8 @@
 		close(2);
 	}
 
+	fd = xopen(bb_dev_null, O_RDWR);
+
 	while ((unsigned)fd < 2)
 		fd = dup(fd); /* have 0,1,2 open at least to /dev/null */