mempool: Test COW vs malloc_init race

mempool: Test COW vs malloc_init race

Test that the entire malloc init value is visible in CPU mappings. If
the COW page copy race vs init happens while init is in the middle of
storing to the newly allocated area, iteration on all CPUs comparing the
visible content to the init value is responsible for detecting and
mitigating uninitialized or partially initialized init value from the
point of view of a CPU. Validate that this scheme has the intended
effect wrt a concurrent COW caused by storing to a nearby per-cpu area
on the same page.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Iebde10eb61e80cc0d8eb0ebc89925f4a2ad9de9c