This is a port of EZP-25396 and related later fixes from 5.4 to master/2017.08.

When editing and publishing new object version with relation fields, the old (obsolete) relations are not cleared.

Steps to reproduce

• Pre-condition: ContentType with relation list field.
• Create a new "Test" content (in eng-GB), add relation to object "A", publish.
• (optional: add a new version in a different language, relate to object "B", publish).
• Add a new version in the main language (eng-GB), modify the relation to use object "A2", publish.

Expected result:

In object's "relations" tab, it should only show "A2" and "B",

Actual result:

In object's "relations" tab, objects "A", "A2" and "B" are shown.

Further Notes:

The behavior seems a regression caused by EZP-24530