Respond to PR code review comments for ported library System.Security.Claims

[venkat-raman251]

@brentschmaltz as the owner of the System.Security.Claims library can you please have a look through the code review comments provided in dotnet/corefx#4933 and address them appropriately.

[weshaggard]

We should also use this to track adding some test coverage for this library.

[karelz]

@steveharter can you please make a list of things that should happen? Or decide all is ok enough.

[steveharter]

I replied to latest feedback

[dotnet-policy-service]

Due to lack of recent activity, this issue has been marked as a candidate for backlog cleanup. It will be closed if no further activity occurs within 14 more days. Any new comment (by anyone, not necessarily the author) will undo this process.

This process is part of our issue cleanup automation.