Fix regression in cursor iterator caused by dfd8ce7

cursor.next was renamed to __next__ for Python 3, with a new function
next that was intended to be a wrapper around it, but it failed to
return the value returned by __next__ :(

Author: kadler

IBM_DB/ibm_db/ibm_db_dbi.py

@@ -1131,7 +1131,7 @@ def __next__( self ):
         return row
 
     def next( self ):
-        self.__next__()
+        return self.__next__()
 
     # This attribute specifies the number of rows the last executeXXX()
     # produced or affected.  It is a read only attribute.