Some public functions in the diskfile manager expect or return full
file paths. It implies a filesystem diskfile implementation.
To make it easier to plug alternate diskfile implementations, patch
functions to take more generic arguments.
This commit changes DiskFileManager _get_hashes() arguments from:
- partition_path, recalculate=None, do_listdir=False
to :
- device, partition, policy, recalculate=None, do_listdir=False
Callers are modified accordingly, in diskfile.py, reconstructor.py,
and replicator.py
Change-Id: I8e2d7075572e466ae2fa5ebef5e31d87eed90fec