LU-16808 lfs: lfs find --printf won't hang on special files

LU-16808 lfs: lfs find --printf won't hang on special files

Add O_NONBLOCK flag on opening special files lest it hang.

Since '--printf' requires gather_all, and in check_projid case and
gather_all case, it open the special file and try to get project id
from it, we shouldn't error out on only gather_all case.

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: Ic2afff7bbccf73ff94c64c62799f9b37b18d10a1
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50905
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Thomas Bertschinger <bertschinger@lanl.gov>