Workaround to Install .NET 3.5 on Windows 2012 R2 in Azure

Fought this error for an absurdly long time today. Found a few error codes after some hunting - 0x800F0906 and 0x800F081F. Seems something is broken in the current image for Windows 2012 R2 DataCenter (version release date of 9/8/2014). Upon trying to add the .NET 3.5 Feature I kept receiving this error

After fighting all kinds of options including reconfiguring my network to use Google DNS services, I finally simply went to Windows Update and added the latest updates. 

Jackpot. That seems to have been it.  Per this blog post it seems there are a handful of hotfixes causing this corruption so the other option would be to go the other way and uninstall the hotfixes listed to get the install to go through too. I tried it out on a new image, and uninstalling KB2966828 let me get .NET 3.5 up and running too.

Hopefully this is resolved in the next image, but until then hopefully this helps someone else save themselves a few hours on a Sunday