ENG-7274: Eliminate the deprecated 'groups' attribute in the user
element in the deployment file.
- Clean up some code that merged both
- Clean up a bunch of other code that used 'group' instead of 'role',
mostly in test code.
- Remove redundant code from RealVoltDB and clean up
Merge pull request #1868 from VoltDB/eng7274

ENG-7274, r=jhugg