Full QuickCheck 2.7 compatibility

Full QuickCheck 2.7 compatibility

This renames the deprecated `printTestCase` to its replacement
`counterexample`, add provides a CPP-guarded fallback for QuickCheck < 2.7.

Signed-off-by: Niklas Hambuechen <niklash@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>

Conflicts:
	test/hs/Test/Ganeti/JQScheduler.hs
          - removed file not present in 2.12
	test/hs/Test/Ganeti/SlotMap.hs
          - removed file not present in 2.12

Cherry-picked-from: 077c415a09f8c381ce788ebe6c065d8ccab60564
Signed-off-by: Petr Pudlak <pudlak@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>