[bug] Fix JavaScript error on django 2.2 #74
[bug] Fix JavaScript error on django 2.2 #74

This commit fixes JS error on django 2.2. Changes:
 - added pointer to `jquery.init.js` in admin.py `Media` classes according to django 2.2 release notes

Fixes #74

openwisp/django-x509,openwisp/django-x509,openwisp/django-x509,openwisp/django-x509