refactor tests use toBeUndefined() function instead of toBe(undefined)

[m-amr]

I am not sure if this important.

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• Do you want to request a feature or report a bug?
  refactor tests Use toBeUndefined() function instead of toBe(undefined)
• What is the current behavior?
  some tests use toBeUndefined() and other use toBe(undefined)
• If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via
  https://plnkr.co or similar (you can use this template as a starting point: http://plnkr.co/edit/tpl:yBpEi4).
• What is the expected behavior?
  use toBeUndefined() for all tests for code consistency
• What is the motivation / use case for changing the behavior?

code consistency

• Which version of Angular, and which browser and OS does this issue affect? Did this work in previous
  versions of Angular? Please also test with the latest stable and snapshot versions.
• Other information (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix)