Fix the glue table in the QP and RBT zone databases

Fix the glue table in the QP and RBT zone databases

When adding glue to the header, we add header to the wait-free stack to
be cleaned up later which sets wfc_node->next to non-NULL value.  When
the actual cleaning happens we would only cleanup the .glue_list, but
since the database isn't locked for the time being, the headers could be
reused while cleaning the existing glue entries, which creates a data
race between database versions.

Revert the code back to use per-database-version hashtable where keys
are the node pointers.  This allows each database version to have
independent glue cache table that doesn't affect nodes or headers that
could already "belong" to the future database version.