v1.7.0-rc.6: MCPClient: ignore deleted derivatives in checksum assignment

Modifies archivematicaUpdateSizeAndChecksum.py so that deleted
derivatives are not mapped to Derivative model instances, thus avoiding
the Django ORM IntegrityError exception bug of 1068.

Fixes #1068

v1.7.0-rc.5: Restore SS's file status check

This commit restores a check we used to make on the returned value of
`storage_service.create_file` because it's possible that the `status` equals to
`FAIL` and if that's the case we should also have the client script fail.

This is in addition to #1049.
It relates to #815.

v1.7.0-rc.4: MCPClient: stop documenting empty dirs in metadata/

Stops the "Normative Directory Structure" logical structMap from
documenting empty directoires in the objects/metadata/transfers/ folder.
Such empty directories are artefacts of Arcivematica's processing and
are not user-created so they should not be documented in this structMap.

Fixes #983

v1.7.0-rc.3

Stop using disableElasticsearchIndexing in MCPClient

v1.7.0-rc.2

Add missing exit code to DIP upload chain link.

v1.7.0-rc.1

Dashboard: add LDAP deps to Dockerfile

v1.6.1-rc5

Archivematica version 1.6.1 Release Candidate 5