Mitigate endless loop broken pipe error

[tb205gti]

The code can end up in an endless loop if a broken pipe is experienced in the _fwrite function. This is a rudimentary mitigation by counting the iterations and comparing it to the buffer_length. If the iterations are double the buffer_length, there is a high risk that it is stuck in an endless loop.

PHP Notice:  fwrite(): send of 2013 bytes failed with errno=32 Broken pipe in /phpMQTT.php on line 435