removed obsolete code and added sync api for producer

Author: and.sergeev

docker/Dockerfile

@@ -6,4 +6,4 @@ ADD . /opt/tarantool
 
 WORKDIR /opt/tarantool
 
-ENTRYPOINT tarantool /opt/tarantool/tests/new_producer.lua
+ENTRYPOINT tarantool /opt/tarantool/tests/producer.lua

kafka/config.lua

@@ -21,6 +21,7 @@ ffi.cdef[[
         void                *key;
         size_t              key_len;
         int64_t             offset;
+        void                *_private;
     } rd_kafka_message_t;
 
     typedef enum rd_kafka_type_t {