[#1714] do not remove session when get_site_user is called

See #1714 for all details. This commit includes only the parts relevant
to 2.2.1.

ckan/logic/action/get.py

@@ -1969,8 +1969,8 @@ def get_site_user(context, data_dict):
         user.sysadmin = True
         model.Session.add(user)
         model.Session.flush()
-    if not context.get('defer_commit'):
-        model.repo.commit_and_remove()
+        if not context.get('defer_commit'):
+            model.repo.commit()
 
     return {'name': user.name,
             'apikey': user.apikey}

ckan/model/__init__.py

@@ -227,6 +227,7 @@ def init_db(self):
         log.info('Database initialised')
 
     def clean_db(self):
+        self.commit_and_remove()
         meta.metadata = MetaData(self.metadata.bind)
         with warnings.catch_warnings():
             warnings.filterwarnings('ignore', '.*(reflection|tsvector).*')