As a Developer I want code related with migration from X-Road v5 to be removed

[VitaliStupin]

Affected components: - Affected documentation: - Estimated delivery: - External reference: https://jira.ria.ee/browse/XTE-337; https://jira.ria.ee/browse/XTE-344

Problem X-Road v6 code currently contains functionality that is meant to simplify transfer from X-Road v5. to v6.. This code is no longer necessary. For example:

• v5 data import in both Central Server and Security Server
• Identifier mapping (v5) in tests
• v6 should not try to restart v5 related services after restore procedure etc.
• removing v5_import table from Central Server (note that after that older backups could not be used for restoring)

Acceptance criteria

• v6 code in cleaned from v5 related functionality

[VitaliStupin]

Fixed in 6.14.0