Bug 7919: Fix unit test (Members_AttributeTypes.t)

Bug 7919: Fix unit test (Members_AttributeTypes.t)

- Reintroduce the class column in a select statement (was present before
  this development)
- FIX UT: If there are no arg passed in parameter, the routine calls
  C4::Context->userenv which call an execute statement. It consumes the
  mocked resultset

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Elliott Davis <elliott@test.bywatersolutions.com>
All tests successful.
Files=1, Tests=9,  0 wallclock secs ( 0.02 usr  0.01 sys +  0.16 cusr  0.06 csys =  0.25 CPU)
Result: PASS