Problem with DeviceMock

At least with Ionic 4.x and @ionic-native 5.x, the `DeviceMock` implementation with plain variables like
```
cordova: string;
```
does not work. There gets called always the original implementation.

But the following works for me:
```
get cordova(): string {
	return "";
}
```

I assume this happens since the properties are originally marked with the decorator `@CordovaProperty`...