Problem
After WT-15527, Followers should never open the live dhandle version of the shared metadata. However opening up as follower we open the live dhandle on __disagg_metadata_table_init. As a short-term fix we immediately expire the live dhandle, to prevent these from happening.

Theoretically speaking, we don't need to create the shared metadata table. Schema operations are first placed in local metadata and then processed on the next checkpoint. However we need more investigation when performing step-up. All schema operations should be equivalent on the shared metadata table.

The layered15 test is a great python test to validate this assumption