schema_load triggers 2nd schema_load (via locking)

Currently, loading the schema (schema_load)
accesses the locking column (locking_column)
which defaults the value (reset_locking_column)
which invalidates the schema (reload_schema_from_cache)
which forces another schema load.

Good news:
The second schema_load does accesses locking_column,
but locking_column is set, so it does not reset_locking_column
and it does not trigger an infinite loop.

The solution is not invalidate the cache while default locking_column

activerecord/lib/active_record/locking/optimistic.rb

@@ -150,7 +150,7 @@ def locking_column=(value)
 
         # The version column used for optimistic locking. Defaults to +lock_version+.
         def locking_column
-          reset_locking_column unless defined?(@locking_column)
+          @locking_column = DEFAULT_LOCKING_COLUMN unless defined?(@locking_column)
           @locking_column
         end