obmc-initfs: shutdown: don't follow links

When creating the synlink for the u-boot-env image, don't
follow any symlinks.

Signed-off-by: Milton Miller <miltonm@us.ibm.com>
diff --git a/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh b/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh
index cc076fd..d29db26 100644
--- a/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh
+++ b/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh
@@ -27,7 +27,7 @@
 if test -s /run/fw_env -a -c /run/mtd:u-boot-env -a ! -e /image-u-boot-env &&
 	! cmp /run/mtd:u-boot-env /run/fw_env
 then
-	ln -s /run/fw_env /image-u-boot-env
+	ln -sn /run/fw_env /image-u-boot-env
 fi
 
 if test -x /update && ls image-* > /dev/null 2>&1