fmq_unit_tests: Detect leaked FDs more efficiently Instead of looping through the max number of allowed FDs +1, we now check the number of FDs opened by the test process before and after creating/destroying a number of queues. Test: atest fmq_unit_tests Bug: 343829026 Change-Id: I9fe29e418b2acafd3a12b1add96ea412e3eaa120