UP-4063 Add trivial unit test.

This is a trivial JUnit test.  Someone should just hit the green Merge button so that uPortal includes just a smidgeon more unit test coverage.

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The origin of this unit test is that I'd written to demonstrate [Coveralls' lovely reporting](https://github.com/apetro/uPortal/pull/1#issuecomment-46627642) on how a pull request will change the test coverage metrics.  Having written this start at unit testing for `PortletAdministrationHelper`, seems worth slurping this into the uPortal codebase and improving test coverage ever so slightly (hey, 0.08% here, 0.08% there, sooner or later you're at 25% test coverage.)

Tests functionality introduced in [UP-4063](https://issues.jasig.org/browse/UP-4063) that `PortletAdminstrationHelper.updateFormForSinglePortletType()` returns `null` when multiple types available.

Obviously, much more than this trivial test could be undertaken to automate testing `PortletAdministrationHelper` against regression, and that'd be nice scaffolding to have in place to support a refactor of that code.