wintun: Revise interface creation wait

DIF_INSTALLDEVICE returns almost immediately, while the device
installation continues in the background. It might take a while, before
all registry keys and values are populated.

Previously, wireguard-go waited for HKLM\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}\<id> registry key
only.

Followed by a SetInterfaceName() method of Wintun struct which tried to
access HKLM\SYSTEM\CurrentControlSet\Control\Network\
{4D36E972-E325-11CE-BFC1-08002BE10318}\<id>\Connection registry key
might not be available yet.

This commit loops until both registry keys are available before
returning from CreateInterface() function.

Signed-off-by: Simon Rozman <simon@rozman.si>

tun/wintun/setupapi/setupapi_windows_test.go

@@ -291,6 +291,11 @@ func TestSetupDiOpenDevRegKey(t *testing.T) {
 			t.Errorf("Error calling SetupDiOpenDevRegKey: %s", err.Error())
 		}
 		defer key.Close()
+
+		_, err = devInfoList.GetInterfaceID(data)
+		if err != nil {
+			t.Errorf("Error calling GetInterfaceID: %s", err.Error())
+		}
 	}
 }