support binding client socket address to specific ifname

[baymaxhuang]

background
In nccl, when we use NCCL_SOCKET_IFNAME to specify which IP interfaces to use for communication, only the listening socket (server side) will bind a specific ifname address. The client socket would use the default address. It would cause some unexpected problems when there are link problems.

Solution
Add a peerAdd in ncclSocket to save peer address of the socket, and the local address is saved in addr. When a client connects to a remote socket (sock->peerAdd), the source address would also be bound to sock->addr.

TODO
Init rasnet client socket with a specific address that rasNetListeningSocket also uses. At present, ncclSocketInit uses nullptr and it would be bound to the default address of the system.