DevDiagnostics: Missing file (loader snaps) button doesn't change from "Enable" when its enabled

[andreww-msft]

Steps to reproduce the bug

1. Run DevDiagnostics.
2. Try to launch the TestLoadFailure test app (this fails to load).
3. See DD creates a new Insight on the Insights page with an "Enable" button to enable loader snaps for the app.
4. Tap Enable.
5. See this does enable loader snaps - try to lauch TestLoadFailure again, and this creates another new Insight with more specific information.
6. But see that the button still says "Enable", where it should probably say "Disable".