Search: Database backend is now default for tests

runtests.py

@@ -67,6 +67,9 @@ if not settings.configured:
         ],
         WAGTAILSEARCH_BACKENDS = {
             'default': {
+                'BACKEND': 'wagtail.wagtailsearch.backends.db.DBSearch',
+            },
+            'elasticsearch': {
                 'BACKEND': 'wagtail.wagtailsearch.backends.elasticsearch.ElasticSearch',
                 'RUN_TESTS': True,
             }