[Fixes #926] Protocol & Host name ignored when creating action link

/cc: @rynowak @dougbu 
also would like to see a unit test (theory) that looks at the `ActionLink()` return value.  this is what we'd likely extend to cover loads more argument values and a few corner cases.  use a mock `IUrlHelper` that just concatenates its parameters.
BTW it's great to see the functional test but we need some unit tests too.
no, I'm not demanding you cover all the corner cases in this PR.  just the starting point is fine.