Change the default connection pool size to 1 (#280)

Author: WeiXinChan

src/main/java/com/alipay/oceanbase/rpc/property/Property.java

@@ -122,7 +122,7 @@ public enum Property {
     RPC_OPERATION_TIMEOUT("rpc.operation.timeout", 2000L, "OB内部执行RPC请求的超时时间"),
 
     // [ObTable][CONNECTION_POOL]
-    SERVER_CONNECTION_POOL_SIZE("server.connection.pool.size", 10, "单个SERVER的连接数"),
+    SERVER_CONNECTION_POOL_SIZE("server.connection.pool.size", 1, "单个SERVER的连接数"),
 
     // [ObTable][NETTY]
     // overwrite the global default netty watermark for ob table: [512K, 1M]