For static builds we still need to manually reorder $HTTP_MODULES, and we
cannot source "auto/module" like the new-style configuration mode needs,
because the "auto/module" snippet modifies $HTTP_MODULES itself, but ignores
the new $ngx_module_order variable when doing a static build.
Fortunately, the old-style way of configuring the module is still working in
all Nginx versions for statically built modules, so we can keep using that
for static builds.
This fixes issue #46.
This avoids potential issues when running the tests in environments which
might set variables which Nginx tries to read on startup. For example,
the $NGINX variable was being picked from the Travis-CI build matrix
configuration.