VIS guardian managed a loaded SDF snapshot for each suspension.
This behavior is useful during commissioning test to use various snapshots.
On the other hand, it's useful to manage loaded snapshots for all models in one place during observing run.

So snapshot management for each suspension is taken over to LSC_LOCK guardian and a function (restore_sdf) is disabled in VIS guardians.
LSC_LOCK guardian will request all models to load down.snap or observation.snap when DOWN or OBSERVATION is requested, respectively during observing run.
(This is same behavior as one in O4a.)