Ceph RBD block driver does not use error_setg_errno() where
it is possible to use. This patch replaces error_setg()
from error_setg_errno().

Signed-off-by: Vikhyat Umrao <vumrao@redhat.com>
Message-id: 1462780319-5796-1-git-send-email-vumrao@redhat.com
Reviewed-by: Josh Durgin <jdurgin@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>