Some tests uses $TRUNCATE to truncate a file.  This explicitly find .../lustre/tests/truncate.

Other tests use "truncate" and assume it is the same program.

One test (sanity 399b) uses "truncate -s", which assumes /usr/bin/truncate.

I'm not really sure how all this works... test_399b fails for me.

The tests should be consistent in which truncate program is used, and how it is called.