Waiting till Socket connection completed (#6909)

After `select` we should use `getsockopt` to read the SO_ERROR option at
level SOL_SOCKET to determine that connection completed successfully

http://man7.org/linux/man-pages/man2/connect.2.html

rb/lib/selenium/webdriver/common/socket_poller.rb

@@ -71,7 +71,7 @@ def listening?
         begin
           sock.connect_nonblock sockaddr
         rescue Errno::EINPROGRESS
-          retry if IO.select(nil, [sock], nil, CONNECT_TIMEOUT)
+          retry if socket_writable?(sock) && conn_completed?(sock)
           raise Errno::ECONNREFUSED
         rescue *CONNECTED_ERRORS
           # yay!
@@ -85,6 +85,14 @@ def listening?
         false
       end
 
+      def socket_writable?(sock)
+        IO.select(nil, [sock], nil, CONNECT_TIMEOUT)
+      end
+
+      def conn_completed?(sock)
+        sock.getsockopt(Socket::SOL_SOCKET, Socket::SO_ERROR).int.zero?
+      end
+
       def with_timeout
         max_time = time_now + @timeout