Revert "Update fulltext search engine to Xapian from Whoosh. (#364)" (#376)

This reverts commit 508da12771.

web/mailman-web/settings.py

@@ -315,13 +315,13 @@ COMPRESS_PRECOMPILERS = (
 #
 HAYSTACK_CONNECTIONS = {
     'default': {
-        # 'ENGINE': 'haystack.backends.whoosh_backend.WhooshEngine',
+        'ENGINE': 'haystack.backends.whoosh_backend.WhooshEngine',
         'PATH': "/opt/mailman-web-data/fulltext_index",
         # You can also use the Xapian engine, it's faster and more accurate,
         # but requires another library.
         # http://django-haystack.readthedocs.io/en/v2.4.1/installing_search_engines.html#xapian
         # Example configuration for Xapian:
-        'ENGINE': 'xapian_backend.XapianEngine'
+        #'ENGINE': 'xapian_backend.XapianEngine'
     },
 }