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.

![screenshot 2013-11-23 22 50 16](https://f.cloud.github.com/assets/785824/1606529/619cd392-5449-11e3-8b91-ee79ae911ed6.png)