RFR(XS) 8055061: assert at share/vm/services/virtualMemoryTracker.cpp:332 Error: ShouldNotReachHere() when running NMT tests

[Zhengyu Gu]

Please review this small fix for tracking CDS mapping. CDS maps whole 
region for its archive, then remaps each section into the region, where 
NMT did not handle this scenario.

Bug: https://bugs.openjdk.java.net/browse/JDK-8055061
Webrev: http://cr.openjdk.java.net/~zgu/8055061/webrev.00/ 
<http://cr.openjdk.java.net/%7Ezgu/8055061/webrev.00/>

Test:
   JPRT on west queue where the problem was discovered.

Thanks,

-Zhengyu