Include --no-network as well as --no-cache in DKL-DI-0004

[philnichol]

As per the thread in this issue, it seems --no-network could be considered equally secure as --no-cache when using apk add, yet Dockle will still mark it as failing DKL-DI-0004.

Just wondering if you'd be open to include --no-network in that check as a pass.

Finally, thanks for your time and for maintaining this awesome project :).