Test for dh_python2 --no-shebang-rewrite directly

Signed-off-by: Dan Mick <dan.mick@inktank.com>
Makefile, conf/httpd: Collapse distro httpd confs into one:

- for all distros, use version >=2.4 for the new Require directive
- put WSGISocketPrefix in dynamically in Makefile

Signed-off-by: Dan Mick <dan.mick@inktank.com>