Support roundtrip in sections 15, 16, 23, & Other
- Remove the backtracking test. It was redundant with PCAP tests, which
already have duplication.
- If possible, modify TDML tests to round trip without changing the
intention of the test.
- Set the defaultRoundTripDefaultDefault to true so that, unless
otherwise specified, all tests will be run round trip. As of this
commit, all tests either round trip successfully, or have explicit set
roundTrip="false" because they are not meant to round trip or there is
a bug preventing them from round tripping.
