[jdk8u-dev] RFR: 8174734: Safepoint sync time did not increase

[SendaoYan]

Hi all,

This backport PR will fix the test bug which cause sun/management/HotspotRuntimeMBean/GetSafepointSyncTime.java intermittent fails. Before this backport , test fails about 1/50 probability. After this backport PR, test run all passed 10k times.

This test was problemlist by [JDK-8174855](https://bugs.openjdk.org/browse/JDK-8174855), this do not backported to jdk8u. So this backport do not need change the jdk/test/Problemlist.txt. And the copyright year different. These two parts cause this backport PR uncleanly. Other parts are all cleanly.

-------------

Commit messages:
 - Backport c83db6b4d13ef015aed654311c10b87e570ac483

Changes: https://git.openjdk.org/jdk8u-dev/pull/734/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=734&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8174734
  Stats: 66 lines in 1 file changed: 38 ins; 17 del; 11 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/734.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/734/head:pull/734

PR: https://git.openjdk.org/jdk8u-dev/pull/734