- Implementation of the ndb_sync_excluded_objects table
- The ndb_sync_excluded_objects table contains information about
  metadata objects whose synchronization has failed due to a
  permanent error and are thus excluded from future mismatch
  detection cycles
- The list of such objects is retrieved from the sync mechanism
  every time the PFS table is queried by a user
- The table contains the schema name, name, and type of the object,
  along with the reason for exclusion. Adding support for the reason
  column involved extending the sync mechanism to store additional
  information during a permanent synchronization failure

Change-Id: I49330fffa4ca115f3e7abf5b16976141debd5dd6