Device state restore get handlers are never called

[jcro]

add_get sets up a get handler to be used to restore device state, adding data to tables get_fptr, get_opaque, get_size, and get_data. These tables are never referenced elsewhere, like in fdl_fast_reload, meaning a subset of device state is not restored when a snapshot is loaded. This can cause VMs to not work correctly (for example by being unresponsive) after a snapshot is restored.

[jcro]

There appear to be a few other related issues.

1. fdl_fast_create_tmp calls the VMSD pre_load and post_load function pointers when creating a tmp snapshot; however this isn't necessary AFAIK. pre_load and post_load only need to be called when loading a snapshot.
2. fdl_fast_create_tmp fails to call the VMSD pre_save function pointer when creating a tmp snapshot.
3. fdl_fast_create_tmp fails to update get handler state when creating a tmp snapshot, so even if the get_fptr stuff mentioned above is addressed, fdl_fast_reload will just load get_fptr device state from the original root snapshot instead of from the tmp snapshot.