LU-4824 utils: lfs find should continue after errors

'lfs find' stops as soon as it encounters an error, such as EACCES.
Change the behavior to match the regular find command: just note the
failure but continue on, returning a non-zero exit code at the end.

Lustre-change: http://review.whamcloud.com/9794
Lustre-commit: 785e7dc56613e79bdfd89fab762eeb82deb7564c

Signed-off-by: Matt Ezell <ezellma@ornl.gov>
Change-Id: I16ca35ec193e36134e7b93d91a20ff1d0778fe60
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/11093
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>