Inherited pipeline hooks are not listed with the `-L` option

[vkarak]

For example, the cscs-checks/prgenv/cuda/cuda_samples.py tests inherit their hook from the base CudaSamples, but this does not show up when listing the concrete tests:

[List of matched checks]
- CudaDeviceQueryCheck:
    Dependencies:
      <none>

    Description:
      CUDA deviceQuery test.

    Environment modules:
      cudatoolkit

    Location:
      /users/karakasv/Devel/reframe/cscs-checks/prgenv/cuda/cuda_samples.py

    Maintainers:
      JO

    Node allocation:
      standard (1 task(s))

    Pipeline hooks:

    Tags:
      external_resosurces, production

    Valid environments:
      PrgEnv-cray, PrgEnv-gnu, PrgEnv-pgi

    Valid systems:
      daint:gpu, dom:gpu, tiger:gpu, arolla:cn, tsa:cn, ault:amdv100, ault:intelv100

Found 1 check(s)