Set DJANGO_SETTINGS_MODULE during deploys.

Freddo, which manages our -dev deploys, is a Django app. When Freddo is
run, it has the environment variable DJANGO_SETTINGS_MODULE set to
accomodate Freddo. Unfortunatly, Kitsune tries to use this value as
well, which messes things up. Kitsune tries to import 'freddo.settings'
when getting Django settings, which fails.

This change resets the environment variable to 'settings_local', which
exists on the kitsune path, and so things succeed.
Gracefully restart apache directly.

Before we touched the `.wsgi` file that controlled the app in order to
signal a reload. This can be problematic, so jakem suggested changing to
this more direct way to reload the app.