LU-11152 test: work around find bug in sanity 133[fg]

LU-11152 test: work around find bug in sanity 133[fg]

Some versions of find do not handle the -ignore_readdir_race option
correctly. Work around this by calling error_ignore() rather than
error() in these cases.

Test-Parameters: trivial

Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I0ad9cef3743f1748908dbab9087b0b54e6466d0a
Reviewed-on: https://review.whamcloud.com/32934
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>