Fix for bug 480363, https://github.com/eclipse/paho.mqtt.c/issues/13

Bug: 480363

src/SSLSocket.c

 /*******************************************************************************
- * Copyright (c) 2009, 2014 IBM Corp.
+ * Copyright (c) 2009, 2016 IBM Corp.
  *
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
@@ -15,6 +15,7 @@
  *    Ian Craggs - fix for bug #409702
  *    Ian Craggs - allow compilation for OpenSSL < 1.0
  *    Ian Craggs - fix for bug #453883
+ *    Ian Craggs - fix for bug #480363, issue 13
  *******************************************************************************/
 
 /**
@@ -447,6 +448,7 @@ void SSLSocket_terminate()
 	FUNC_ENTRY;
 	EVP_cleanup();
 	ERR_free_strings();
+	CRYPTO_set_locking_callback(NULL);
 	if (sslLocks)
 	{
 		int i = 0;