LU-2783 ofd: Implement OBD_IOC_GET_OBJ_VERSION

This patch implements OBD_IOC_GET_OBJ_VERSION for ofd, so that tests
can use "lctl getobjversion" on OST objects.  jt_get_obj_version() now
takes ID and group pairs, as well as FIDs, for OST objects.  Although
the code are for testing purposes only, dereferencing an ioc_inlbuf
without checking its size is still unacceptable.  Hence,
mdt_ioc_version_get() is changed to check sizes first.

Signed-off-by: Li Wei <wei.g.li@intel.com>
Change-Id: If259aeca281dcb3f4ee4dc719719f722cf72cad4
Reviewed-on: http://review.whamcloud.com/5467
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>