Runs memory leak detection even if unwanted, discarding output

I'm running tests under DrMemory to find leaks, and find that the builtin leak detection interferes with that so I'd like to turn it off. I've tried

set BOOST_DETECT_MEMORY_LEAK=0

which hides the output, but the process still spends a minute below `_CrtDumpMemoryLeaks` during shutdown, after printing results. Running under DrMemory, that often extends to an hour, causing timeouts.

I'd expect VS based memory leak debugging to be disabled completely in this case.