Remove unneeded LD_PRELOAD setting in fsa unit tests.
Remove unneeded LD_PRELOAD setting in fsa unit tests.

vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa