Flush column family

[GalRogozinski]

Description

Delete column family correctly

Fixes #1482

Type of change

• Bug fix (a non-breaking change which fixes an issue)

How Has This Been Tested?

Ran on dry with rescan
Will be farther validated by the reviewer

Checklist:

• My code follows the style guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[karimodm]

Alright, this PR will specifically fix the OOMs caused by:

        if (configuration.isRevalidate()) {
            tangle.clearColumn(com.iota.iri.model.persistables.Milestone.class);
            tangle.clearColumn(com.iota.iri.model.StateDiff.class);
            tangle.clearMetadata(com.iota.iri.model.persistables.Transaction.class);

Let's go ahead and merge

[GalRogozinski]

@karimodm
maybe it is unlikely but could the revalidate issue you had could be related to this?

[karimodm]

This PR is probably introducing a database corruption upon --revalidate. Please refer to #1391

[GalRogozinski]

@karimodm
just to be clear, did you test again without the PR and you noticed that there is no corruption?