use existing encoder object

Author: mambocab

cassandra/metadata.py

@@ -1435,7 +1435,7 @@ def as_cql_query(self):
                 index_target,
                 class_name)
             if options:
-                opts_cql_encoded = Encoder().cql_encode_all_types(options)
+                opts_cql_encoded = _encoder.cql_encode_all_types(options)
                 # PYTHON-1008
                 if isinstance(opts_cql_encoded, six.binary_type):
                     opts_cql_encoded = opts_cql_encoded.decode('utf-8')