RFR: JDK-8270156: Add randomness and stress keys to JTreg tests which use StressGCM, StressLCM and/or StressIGVN

[Tobias Holenstein]

Added the keys "randomness" and "stress" to the JTreg tests which use StressGCM, StressLCM and/or StressIGVN and did not use the keys before.

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Commit messages:
 - JDK-8270156: Add randomness and stress keys to JTreg tests which use StressGCM, StressLCM and/or StressIGVN

Changes: https://git.openjdk.java.net/jdk/pull/5614/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5614&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8270156
  Stats: 10 lines in 8 files changed: 8 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5614.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5614/head:pull/5614

PR: https://git.openjdk.java.net/jdk/pull/5614