Disallow copy and assign of Channel

[chenBright]

What problem does this PR solve?

Issue Number:

Problem Summary:

禁用Channel拷贝和赋值操作：

1. 拷贝得到Channel并一定能使用（不知道是否Init）
2. 拷贝后，未再次执行SocketMapInsert令_server_id的引用计数加一。这样，只要有一个Channel析构了，就会将_server_id从SocketMap里删除，其他Channel副本的RPC调用都会失败。

What is changed and the side effects?

Changed:

Side effects:

• Performance effects(性能影响):

• Breaking backward compatibility(向后兼容性):

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Check List:

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