[jdk13u-dev] RFR: 8236617: jtreg test containers/docker/TestMemoryAwareness.java fails after 8226575

[Ekaterina Vergizova]

I'd like to backport 8236617 to 13u as follow-up fix for 8226575 that is already included to 13u.
The patch doesn't apply cleanly due to the context difference in TestMemoryAwareness.java 
(getTotalMemorySize() and getFreeMemorySize() methods are not added to OperatingSystemMXBean in 13u by 8226575), reapplied manually.
Tested with container tests, the affected test passed.

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Commit messages:
 - Backport 44f7fe57a8e90f31875bb50cd55eaf4d57b1a6f6

Changes: https://git.openjdk.java.net/jdk13u-dev/pull/34/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk13u-dev&pr=34&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8236617
  Stats: 17 lines in 2 files changed: 6 ins; 0 del; 11 mod
  Patch: https://git.openjdk.java.net/jdk13u-dev/pull/34.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk13u-dev pull/34/head:pull/34

PR: https://git.openjdk.java.net/jdk13u-dev/pull/34