Fix path (fio config and the output file)

Add AP and LP in Utils module
which converts given path to Absolute (from the caller's initial
location) path and to lib/dmtest/${path} respectively.

Writeboost runs its three tests without failure now.
Also, fixed the things for dm-cache and bcache.
Merge pull request #5 from akiradeveloper/feature/fix-fio-path-to-run-writeboost-test

Fix path (fio config and the output file)