* instead of making (dis)-allow 0.9 a property of connection info,
work off a state machine that engages in the liberal skipping of
junk before response headers only immediately after a no-content
response on the same connection.
* when scanning for response headers in a large amount of junk place a
non infinite limit on that (128KB).. the only known use case for
this is skipping illegal message bodies in 304's and those just
aren't that big.
that do_test_finished is called even when an exception is thrown.
Also make the test work in the presence of PAC, where the channel changes
between asyncOpen and onStartRequest.
r=bz a=test-only
