Add testTransportTypesEqual to dnsmanager test cases

A test that ensures that NetworkCapabilities.TRANSPORT_* is eaual
to IDnsResolver.TRANSPORT_* for every possible value of each.

Bug: 153267602
Test: atest FrameworksNetTests
Merged-In: I6b23ccc6ce1659fdfd9573dfcd895f2c20fa9417
Change-Id: I3dd4ed0d1fcceca9c8aec9b3e6769603e4fa913b
(cherry picked from commit 5f28e6f8)