tls: destroy singleUse context immediately

Destroy singleUse context right after it is going out of use.

Fix: #1522
PR-URL: #1529
Reviewed-By: Shigeki Ohtsu <ohtsu@iij.ad.jp>

Author: indutny

lib/_tls_common.js

@@ -134,8 +134,10 @@ exports.createSecureContext = function createSecureContext(options, context) {
   }
 
   // Do not keep read/write buffers in free list
-  if (options.singleUse)
+  if (options.singleUse) {
+    c.singleUse = true;
     c.context.setFreeListLength(0);
+  }
 
   return c;
 };

lib/_tls_wrap.js

@@ -301,7 +301,9 @@ TLSSocket.prototype._wrapHandle = function(handle) {
 };
 
 TLSSocket.prototype._destroySSL = function _destroySSL() {
-  return this.ssl.destroySSL();
+  this.ssl.destroySSL();
+  if (this.ssl._secureContext.singleUse)
+    this.ssl._secureContext.context.close();
 };
 
 TLSSocket.prototype._init = function(socket, wrap) {