virtual cluster port assign support port conflict detect

[village-way]

What would you like to be added:

Why is this needed:

1. linux port range: 32768-60999 used for extempore port, this is conflict with virtual cluster port range
2. We should ensure that the port is available when allocating it.

• node-agent add api for port avaliable check @village-way
• virtual cluster port assign should invoke node-agent api when assign port @OrangeBao

[duanmengkk]

/reopen