Replace mock by unittest.mock in 2 forgotten cases

We replaced usage of third party mock by the standard library in:
https://review.opendev.org/#/c/721021/
There are 2 forgotten occurrences where we still use the third
party mock, the patch fixes that.

Change-Id: I7d00be25bb0b70ce55e27790df33d9134c2a52ae
2 files changed