btrfs-progs: cleanup after errors in open_file_or_dir3

We should zero the dirstream in case we close it ourselves, so the
caller does not do it again. Most current callers do not do that and
exit immediatelly.

Signed-off-by: David Sterba <dsterba@suse.cz>

utils.c

@@ -1915,8 +1915,10 @@ int open_file_or_dir3(const char *fname, DIR **dirstream, int open_flags)
 	}
 	if (fd < 0) {
 		fd = -1;
-		if (*dirstream)
+		if (*dirstream) {
 			closedir(*dirstream);
+			*dirstream = NULL;
+		}
 	}
 	return fd;
 }