Add backends and simulated TPM device

Signed-off-by: Ettore Di Giacinto <edigiacinto@suse.com>

backend/socket.go

@@ -0,0 +1,13 @@
+package backend
+
+import "net"
+
+func Socket(f string) (*FakeTPM, error) {
+	conn, err := net.Dial("unix", f)
+	if err != nil {
+		return nil, err
+	}
+	return &FakeTPM{
+		ReadWriteCloser: conn,
+	}, nil
+}