security/py-{acme,certbot}: fix missing dependency on py-mock

Common:

• Move py-mock requirement to dev_extras in setup.py
• Bump PORTREVISION

PR: 220274
Submitted by: cpm
Reported by: Randy Westlund <rwestlun@gmail.com>
Approved by: koobs (maintainer, py-certbot)
MFH: 2017Q2