Merge pull request #1543 from yahonda/address_ora_1027

Address `MigrationTest#test_create_table_with_query_from_relation` error

Author: yahonda

lib/active_record/connection_adapters/oracle_enhanced/schema_creation.rb

@@ -37,7 +37,7 @@ def visit_TableDefinition(o)
               end
             end
             add_table_options!(create_sql, table_options(o))
-            create_sql << " AS #{@conn.to_sql(o.as)}" if o.as
+            create_sql << " AS #{to_sql(o.as)}" if o.as
             create_sql
           end