fix add_dev() handling of broken links

Resolves issues like:
mdadm -Ss
mdadm: unable to open /dev/md/r1: No such file or directory

...where /dev/md/r1 points to a removed device.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

util.c

@@ -467,8 +467,10 @@ int devlist_ready = 0;
 int add_dev(const char *name, const struct stat *stb, int flag, struct FTW *s)
 {
 	struct stat st;
+
 	if (S_ISLNK(stb->st_mode)) {
-		stat(name, &st);
+		if (stat(name, &st) != 0)
+			return 0;
 		stb = &st;
 	}