Correct isThirdParty check

Previously, isThirdParty check was over-selecting for third-party-ness,
the only non-third-party paths were those explicitly excluded from
typically third party directories, results in ~all code being considered
third party.

Updated test to ensure bionic is not considered third party, which fails
without this change.

Test: go soong tests
Change-Id: Id371aaad2ceef2b3163384fa84712397877cbe90