shim: Create address file with 0644 permissions

Fixes ae70213

In ae70213 the WritePidFile and WriteAddress functions were
changed to use AtomicFile instead of os.CreateFile. However,
AtomicFile creates a temporary file and then changes its permissions
with os.Chmod which alters the previously observed behavior of
os.CreateFile which takes the system's umask into account.

This means that on Linux-based systems these files suddenly
became world writable (#9363).

Signed-off-by: Jaroslav Jindrak <dzejrou@gmail.com>

runtime/v2/shim/util.go

@@ -144,7 +144,7 @@ func WriteAddress(path, address string) error {
 	if err != nil {
 		return err
 	}
-	f, err := atomicfile.New(path, 0o666)
+	f, err := atomicfile.New(path, 0o644)
 	if err != nil {
 		return err
 	}