PROBLEM:
- In current version pattern for naming hidden dropped column has
  changed.
- When cfg file is taken from older version hidden dropped column
  name follows old pattern.
- When INSTANT operations are done in current version exactly in same
  order as done before creating cfg file, then the server crashes.

FIX:
- When searching dropped column with older name version returns null,
  IMPORT fails with error SCHEMA_MISMATCH.

Change-Id: Ifd93adafb78f0aa7b5ae1980b64a3230f94deae9