LU-1406 ofd: OFD device methods

LU-1406 ofd: OFD device methods

Add capability code and basic device functions: statfs, set_info,
get_info, iocontrol, ping, sync, health_check

Signed-off-by: Mikhail Pershin <tappro@whamcloud.com>
Change-Id: I7a0a671ef45e8f4860344bd8c9a9a306d60bd780
Reviewed-on: http://review.whamcloud.com/2856
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>