RFR: JDK-8271252: os::reserve_memory should not use mtOther as default NMT flag

[Evgeny Astigeevich]

On Sat, 25 Jun 2022 05:39:03 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> Small cleanup.
> 
> We use mtOther as default NMT flag for os::reserve_memory():
> 
> `static char* reserve_memory(size_t bytes, bool executable = false, MEMFLAGS flags = mtOther);`
> 
> mtOther marks allocations coming from outside the VM. It is not a good default flag. Note that in the end mtOther then was ignored in os::reserve_memory() and it defaulted to mtNone anyway.
> 
> This trivial patch straightens the logic and uses `mtNone` as default. Note that since mtOther was ignored before, there is no behavioral change.

Except the title, lgtm.

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PR: https://git.openjdk.org/jdk/pull/9287