LU-6732 llite: ll_write_begin/end not passing on errors

LU-6732 llite: ll_write_begin/end not passing on errors

Because of a implementation of generic_perform_write(), write(2)
may return 0 with no errno even if EDQUOT or ENOSPC actually
happend in it.
This patch fixes the issue with setting a proper errno to
ci_result and get it in ll_file_io_generic.

Signed-off-by: Hiroya Nozaki <nozaki.hiroya@jp.fujitsu.com>
Change-Id: I3fc986b57d703ad5fbf41e1ea8182d2d561e8005
Reviewed-on: http://review.whamcloud.com/15302
Tested-by: Maloo <hpdd-maloo@intel.com>
Tested-by: Jenkins
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>