Remove LACOUNT and LACCESSOR and migrate the records immediately.
This concept didnt work out and it is really just as expensive as a full migration
anyway, without the benefit of caching the data for subsequence accesses.
Now, migrate the records immediately on first access.
This will be combined with a "cheap vacuum-lite" for special empty records to
prevent growth of databases.
Later extensions to mimic read-only behaviour of records will include proper shared read-only locking of database records, making the laccessor/lacount read-only access to the data obsolete anyway.
By removing this special case and handling of lacount laccessor makes the codapath where shared read-only locking will be be implemented simpler, and frees up space in the ctdb_ltdb header for use by vacuuming flags as well as read-only locking flags.