staging: lustre: 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
happened in it. This patch fixes the issue with setting a proper
errno to ci_result.

Signed-off-by: Hiroya Nozaki <nozaki.hiroya@jp.fujitsu.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6732
Reviewed-on: http://review.whamcloud.com/15302


Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>