RFR: NMT: Don't record uncommits unconditionally

[coleen.phillimore at oracle.com]

Seems good.
Coleen

On 1/10/18 11:01 AM, Stefan Karlsson wrote:
> Hi all,
>
> Please review this patch to fix a bug in the recent NMT implementation 
> for ZGC.
>
> http://cr.openjdk.java.net/~stefank/zgc/zNMTBugFix/webrev.01
>
> The uncommit path was executed even when NMT was turned off. Because 
> of this we hit the following assertion when pages were detached:
>
> #  Internal Error (.../services/memTracker.hpp:231), pid=12751, tid=2738
> #  assert(tracking_level() >= NMT_summary) failed: Check by caller
>
> Thanks,
> StefanK