Get rid of inifinity retry loop in Socket.udp_server_sockets

* ext/socket/lib/socket.rb (Socket.udp_server_sockets): remove duplicated
  addresses before passing it to ip_sockets_port0 because it causes
  Errno::EADDRINUSE and retry forever.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58293 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/socket/lib/socket.rb

@@ -897,6 +897,7 @@ class Socket < BasicSocket
         ip_list << ai
       end
     }
+    ip_list.uniq!{|e| e.to_sockaddr}
 
     if port == 0
       sockets = ip_sockets_port0(ip_list, false)