ensure last comma removed in select

* We strip out the json select fields in our tests since it is an sql
lite database underneath. Ideally, we would do something fancier, but we
aren't. In doing this stipping, we could strip the last element in the
projection list. This would result in an extra dangling comma. This
commit removes the danging comma in the projection list after the
removal of JSON projections.

awx/main/tests/functional/analytics/test_collectors.py

@@ -36,6 +36,8 @@ def sqlite_copy_expert(request):
         for line in sql.split('\n'):
             if line.find('main_jobevent.event_data::') == -1:
                 sql_new.append(line)
+            elif not line.endswith(','):
+                sql_new[-1] = sql_new[-1].rstrip(',')
         sql = '\n'.join(sql_new)
 
         self.execute(sql)