ClassAd references don't handle My properly. #4759

When calulating the internal references of a ClassAd expression,
attribute references that include 'My.' weren't followed properly. The
named attribute was included in the list of internal references, but any
attributes it refered to were missed.
Improve ClassAds unit tests for internal references via My. #4759

When calculating internal references, check that attributes prefixed
with 'My.' are recursed through properly.