LU-3285 mdc: add cl_device to the MDC

LU-3285 mdc: add cl_device to the MDC

Introduce cl_device for MDC so it is able to prepare and send
IO requests to the MDT.

This patch adds basic interfaces for device and object methods.
The common code is exported from OSC for MDC.

Change-Id: I1834f6d59751599acbcc18a7e2f2a31fa560bb41
Signed-off-by: Mikhal Pershin <mike.pershin@intel.com>
Reviewed-on: https://review.whamcloud.com/28009
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>