Remove deprecated oslotest.mockpatch usage
Remove deprecated oslotest.mockpatch usage

It is deprecated[1] and will be removed soon.

[1] https://docs.openstack.org/oslotest/latest/reference/api/oslotest.mockpatch.html

Change-Id: I06f12724c7e64057f1c5971f4847f878a3f87a51
Closes-Bug: #1712017

openstack/bilean,openstack/bilean