Having Visual Studio 2017 Preview installed breaks engine associaition with VS

If Visual Studio 2017 is currently installed and the preview version is installed alongside it, Setting Editor Preferences>Source Control>Source Code Editor to Visual Studio 2017 will always open the Preview version of VS.

Additionally, if the preview is later uninstalled, the editor will only open VS2015, even if Source Code Editor is set to Visual Studio 2017. Locally this also caused the VS2015 splash to not display properly when opening.

1. Ensure Visual Studio 2015 / 2017 / 2017 Preview are installed
2. Open UE4 Editor (any project)
3. Set Editor Preferences>Source Control>Source Code Editor to Visual Studio 2017
4. Add code to project / File>Open Visual Studio 2017

Result:
If the preview is installed, the editor will always open the preview over the release. If the preview version is uninstalled, 2015 will launch instead of 2017