改进flume使用thrift的方式，增加连接池管理thriftclient，并做到坏死节点检测
	renamed:    ../consumer/flume_client.go -> ../consumer/client/flume_client.go
	renamed:    ../consumer/flume_client_test.go -> ../consumer/client/flume_client_test.go
	modified:   ../consumer/log_sink.go
	modified:   ../consumer/log_sink_test.go
	modified:   ../consumer/option.go
	new file:   ../consumer/pool.go
	new file:   ../consumer/pool_test.go