fmq_unit_tests: Detect leaked FDs more efficiently am: 8676f1dbd6

Original change: https://android-review.googlesource.com/c/platform/system/libfmq/+/3108669

Change-Id: Ie01aedc09d0640caaf897b917fa2a114ff6f8148
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>