Add comment to tsan-suppressions.txt describing why we suppress deadlock warning related to attribute context lock and enumerated attribute enum lock.
Add comment to tsan-suppressions.txt describing why we suppress
deadlock warning related to attribute context lock and enumerated
attribute enum lock.

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