tests: add all missing b prefixes in reactor tests
Both of these tests now pass on Python 3.
# skip-blame just b prefixes. So many b prefixes.
Differential Revision: https://phab.mercurial-scm.org/D3369
stringutil: ast.literal_eval needs a unicode on py3
Fortunately for us, this is really only used internally, so we can be
lazy about the encoding here.
test-wireproto-framing.py now passes on Python 3.
Differential Revision: https://phab.mercurial-scm.org/D3368