testBackendMethodPost fails on php 5.4

We use array_diff to compare ...

    $this->assertEquals(array_diff(array (
  'x' => 'y',
  'data' =>
  array (
    'a' => 1,
    'b' => 2,
  ),
), $parsed['object']), array());

In php 5.4 this test gives a failure:

There was 1 error:

1) backendCase::testBackendMethodPost
Array to string conversion

The actual content of $parsed['object'] is:

Array
(  
    [x] => y
    [data] => Array
        (  
            [a] => 1
            [b] => 2
        )

    [#id] => @none
)

So the "[#id]" key is something we only get in php 5.4?

Related: https://drupal.org/node/1511396#comment-6246736
and #1850798: Add a recursive version of array_diff_assoc()

I first tried to use the drupal_array_diff_assoc_recursive() for this test, but realized it could be simplified.
With the attached patch we get a proper failure in php 5.4.4, on 5.3.10 the test still passes.

There was 1 failure:

1) backendCase::testBackendMethodPost
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
 Array (
     'x' => 'y'
     'data' => Array (...)
+    '#id' => '@none'
 )

/home/helmo/src/drush/tests/backendTest.php:212
/home/helmo/src/drush/vendor/phpunit/phpunit/phpunit.php:46

FAILURES!
Tests: 1, Assertions: 2, Failures: 1.

Summary: This improves the failure... now we can look for a fix.