QLS: statically enable/disable fault injection depending on the SUT

Faults can only be injected into a mocked HasFS, but not all the SUTs we test
use a mocked HasFS. If the SUT does not make use of a mocked HasFS then the
result of fault injection will always be InjectFaultAccidentalSuccess. This PR
adds some boilerplate for statically enabling/disabling fault injection
depending on the SUT.

Fault injection is then enabled for the following SUTs:
* The "real" implementation in IO using a mocked HasFS
* The "real" implementation in IOSim using a mocked HasFS

Fault injection is then disabled for the following SUTs:
* The reference implementation: it does not use a HasFS
* The "real" implementation in IO using the real HasFS: it uses the real file
  system

Author: jorisdral