Most validateFeatureFlags() checks malfunction when installing a snap from the store

[James Henstridge]

The validateFeatureFlags() function in overlord/snapstate/snapstate.go is intended to block the install of snaps that use experimental features that are not enabled on the target system.

However, a number of those checks only seem to work correctly when installing a snap from the file system. When installing from the store, the function is passed a snap.Info struct that has been partially filled with information from the store by infoFromStoreInfo().

In particular, info.Layout and info.Apps are nil, so the checks for the layouts, user-daemons, and dbus-activation features will never fail. Out of these, user-daemons is the only feature that isn't yet enabled by default, so it's the

This was discovered with respect to the firmware-updater snap, which can be installed with "snap install firmware-updater" but fails if downloaded and installed from a path. This failure also occurs when the snap is seeded.