RFR: 8146115 - Improve docker container detection and resource configuration usage

[Bob Vandette]

Please review these changes that improve on docker container detection and the
automatic configuration of the number of active CPUs and total and free memory
based on the containers resource limitation settings and metric data files.

http://cr.openjdk.java.net/~bobv/8146115/webrev.00/ <http://cr.openjdk.java.net/~bobv/8146115/webrev.00/>

These changes are enabled with -XX:+UseContainerSupport.

You can enable logging for this support via -Xlog:os+container=trace.

Since the dynamic selection of CPUs based on cpusets, quotas and shares
may not satisfy every users needs, I’ve added an additional flag to allow the
number of CPUs to be overridden.  This flag is named -XX:ActiveProcessorCount=xx.


Bob.