Merge branch '373' of https://github.com/eclipse/paho.mqtt.c.git into 373

* '373' of https://github.com/eclipse/paho.mqtt.c.git:
  Forgot to remove test failure code!
  Make sure writeComplete deals with socket error #373
  Some corrections for failing socket writes #385
  Take account of not finding a response in writeComplete #385
  Add another continuous write test
  Add continuous send test
  More memory cleanup on network errors - #373