net: fix asserts

Fixes a 'Converting circular structure to JSON' TypeError.

lib/net.js

@@ -375,7 +375,7 @@ Socket.prototype.destroy = function(exception) {
 function onread(buffer, offset, length) {
   var handle = this;
   var self = handle.owner;
-  assert.equal(handle, self._handle);
+  assert(handle === self._handle, 'handle != self._handle');
 
   timers.active(self);
 
@@ -722,7 +722,7 @@ function afterConnect(status, handle, req, readable, writable) {
     return;
   }
 
-  assert.equal(handle, self._handle);
+  assert(handle === self._handle, 'handle != self._handle');
 
   debug('afterConnect');