[DMN Designer] Clear command caches context entries

This issue was spotted during review of DROOLS-2392, however relation is not probable between both.

If user clears the top level context entry and then select same context entry exactly the same context entry will appear. There should appear context entry with default values.

Acceptance test

1. check scenario described in PR comments
2. check scenario from DROOLS-2424
3. check scenario form DROOLS-2425
4. Steps to reproduce fixed - Clear the context entry at depth:
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