Unit test for SecurityBindingElement.KeyEntropyMode.

[imcarolwang]

For #3860.

@StephenBonikowsky , @mconnew , @HongGit

[StephenBonikowsky]

Looks good to me, the default value is the same as on full framework.

[imcarolwang]

@StephenBonikowsky this was not merged and I happen to found I am able to do the merge operation, so I merged it ...

[StephenBonikowsky]

In this case that's fine, but for future PRs I want to get Matt's signoff as well. So if you have a PR that both he and I have approved and the checks are green then go ahead and merge.

You also need to do a couple other things once you merge which it looks like you did in this case...

• move the related work item to the 'Scenario Tests' pipeline.
• edit the description and check off the unit test field.
• un-assign the work item

Thanks!

[imcarolwang]

Ok :)