Follow up socket.tcp_connect() fixing

This patch fixes tcp_connect() for case when server sends
some data immediately after connect.

src/lua/bsdsocket.lua

@@ -891,11 +891,17 @@ local function tcp_connect_remote(remote, timeout)
         box.errno(save_errno)
         return nil
     end
-    if s:wait(timeout) ~= 'W' then
-        -- When the connection completes succesfully, the descriptor becomes
-        -- writable. When the connection establishment encounters and error,
-        -- the descriptor becomes both readable and writable (Stevens UNP).
+    res = s:wait(timeout)
+    save_errno = s:errno()
+    -- When the connection completes succesfully, the descriptor becomes
+    -- writable. When the connection establishment encounters an error,
+    -- the descriptor becomes both readable and writable (Stevens UNP).
+    -- However, in real life if server sends some data immediately on connect,
+    -- descriptor can also become RW. For this case we also check SO_ERROR.
+    if res ~= nil and res ~= 'W' then
         save_errno = s:getsockopt('SOL_SOCKET', 'SO_ERROR')
+    end
+    if save_errno ~= 0 then
         s:close()
         box.errno(save_errno)
         return nil