pkg/adt: interval tree based on rbtree

[xkeyideal]

Please read https://github.com/etcd-io/etcd/blob/master/CONTRIBUTING.md#contribution-flow.

[gyuho]

Please make this Fatalf:

etcd/pkg/adt/interval_tree_test.go

Line 301 in 9a2af73

t.Logf("level order after deleting '11' expected %v, got %v", expectedAfterDelete11, visitsAfterDelete11)

[xkeyideal]

@gyuho I didn't change the interval_tree_test.go file

[gyuho]

@xkeyideal I meant, we should change this to Fatalf with this PR, so we can validate the fix

etcd/pkg/adt/interval_tree_test.go

Line 301 in 9a2af73

t.Logf("level order after deleting '11' expected %v, got %v", expectedAfterDelete11, visitsAfterDelete11)

If this fix is correct, it will pass. If not, it will fail.

[xkeyideal]

@gyuho has changed

[gyuho]

@xkeyideal Awesome. Thanks for the contribution!

[gyuho]

This fix is merged as 003362e.

Thanks @xkeyideal !

[jingyih]

@xkeyideal Thanks!

[jingyih]

@gyuho I think we need to backport this? Also update the changelog? Feel free to assign me.

[gyuho]

@jingyih Already backported :)

[gyuho]

I meant, backported to 3.4 branch. Not yet for 3.3. Let's run tests during our 3.4 release cycle. If it looks good, we can backport 003362e to 3.3