Quiet some noisy loggers for lettuce acceptance tests

[jzoldak]

This will suppress some of the log messages that are clogging up the logs and confusing people who are troubleshooting actual errors:

• Cannot determine primary key of logged in user
• Cannot find corresponding link for name: TOS
• Cannot find corresponding link for name: PRIVACY

[auraz]

👍
Do you think it will be good idea to have common_acceptance.py to avoid duplication in cmd and lms acceptance.py files?

[jzoldak]

Yeah @auraz it does look like the files could stand some refactoring. I'll merge this for now and put that thought on the backlog.