Revert "Upgrade python/mock to 4.0.2"

This reverts commit 73ebb2ed5b2c2548259190bcbec2136f25598ec6.

Reason for revert: The CL caused acloud unittest fail. (b/151394661)

Bug: 151394661
Bug: 151400302

Change-Id: I174b84067f892cb343abdc3a3aebd90cd1ddb0d3
30 files changed