Avoid Warning message on rabbit server down and E_STRICT mode

Hi,

After testing this lib in E_STRICT mode PHP 5.4 I found that this gives a warning message when our rabbit server is down. I saw you perform a check if  ```$this->sock``` is null but before this PHP gives an this annoying warning message.

If you put a silent ```@``` before stream_socket_client you can remove the warning and continue with the exception working perfectly.

I'd like to add this to your code.

Thank you very much