t/fiotestlib: use dictionaries for filenames and paths

t/fiotestlib: use dictionaries for filenames and paths

Instead of separate variables for all the different filenames and paths,
use dictionaries for the filenames and paths.

This involves changing the function signature for the constructor and
setup() functions so that parameters are passed to setup() instead of
the constructor. This is because the base class defines the filenames
dictionary but FioJobFileTest needs to put an entry into the dictionary
before calling the base class constructor.

Signed-off-by: Vincent Fu <vincent.fu@samsung.com>