Revert "Merge varunsharma/buildbot:master (PR #1097)"

This reverts commit c39caeed39c251f15d4a0102cee1a5af95778d49, reversing
changes made to 66784b87b7991f470f9dce5206894737e154c3aa.
Rename props.has_propkey back to props.has_key

This was renamed in 03e1d28, but that was too much.  Pep8 was only
complaining about calls to has_key when 'in' is better.