Use unittest.mock instead of third party mock

Now that we no longer support py27, we can use the standard library
unittest.mock module instead of the third party mock lib.

Change-Id: If1de2f48da1fd6ed3f96c98b8dce9eace4f8095d
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>
38 files changed