libfmq: Fix double closing fd in rust binding

In convertHandle, dup the provided fd before putting it into
ScopedFileDescriptor. In the case of MessageQueue::from_desc, the fd is already owned by NativeHandle so it will be closed twice without dup.

Bug: 348328714
Change-Id: I4785b2c5f6883984ed4d1822ba64db74c17a1892
Test: atest --host fmq_unit_tests