Properly expectDeprecation when test parameter is a function

`Ember.deprecate` is called with `(message, test, options)`. When
`test` is falsy or a function that evaluates to falsy, the deprecation
is issued.

`expectDeprecation` was correctly evaluating the `test` param when it is
a function, but not pushing the correct result of that function into
`actuals`. This made using `expectDeprecate` fail for a deprecation that used
a test function.

Example:

```
// Ember code
function foo() {
  Ember.deprecate('message', function() { return false; });
}

// test code -- this test would erroneously fail because
// expectDeprecation pushes ['message', function() { return false; }]
// onto actuals instead of ['message', false]
expectDeprecation(function() {
  foo();
}, 'message');
```

addon/test-helper/deprecation.js

@@ -23,11 +23,12 @@ DeprecationAssert.prototype = {
     }
     var assertion = this;
     this.env.Ember.deprecate = function(msg, test) {
-      var pushDeprecation = typeof test === 'function' ? !test() : !test;
+      var resultOfTest = typeof test === 'function' ? test() : test;
+      var shouldDeprecate = !resultOfTest;
 
       assertion.actuals = assertion.actuals || [];
-      if (pushDeprecation) {
-        assertion.actuals.push([msg, test]);
+      if (shouldDeprecate) {
+        assertion.actuals.push([msg, resultOfTest]);
       }
     };
   },