System.Runtime.Serialization.Xml test failure on OSX

[jiayi11]

A DataContract Serializer serializing deeply linked list test was added in this pr. However, the test fails on OSX with StackOverFlow exception. Failed build status can be found here. We already disabled the test on OSX, but still need to investigate the reason of the failure.

[StephenBonikowsky]

@imcarolwang Could you create a PR removing the skip attribute on this test to see if the test still fails. There should be a "Do Not Merge" or similar label you can put on the PR to make sure it doesn't get merged.

[imcarolwang]

Case still fail with Stack Overflow error on OSX in the PR build checks, but it doesn't repro when I run the standalone test app on our own osx10.12 locally.