tests: ignore http tests that are known wontfix failures on python 2.4
As mentioned on http://bz.selenic.com/show_bug.cgi?id=2739#c17 , b3083042bdda
left test-http.t failing on Python < 2.4.3. That has not been noticed because
most 2.4 testing has been done with a patched 2.4.2.
This makes sure that the tests only are run for Python >= 2.4.3. That makes it
possible to verify that everything else works with Python 2.4.
[ original upstream message ]