RFR: 8269478: Shenandoah: gc/shenandoah/mxbeans tests should fail when no notifications arrive [v2]

[Aleksey Shipilev]

> After JDK-8259954, some mxbeans tests wait in the effectively infinite loop for the notifications to arrive. If notifications are broken, it would wait forever, and test would timeout. We need to make such failure mode more straightforward.
> 
> Additional testing: 
>  - [x] Linux x86_64 fastdebug `gc/shenandoah/mxbeans` 
>  - [x] Linux x86_64 fastdebug `gc/shenandoah/mxbeans`, `-Xcomp`

Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into JDK-8269478-sh-mxbeans-tests
 - 8269478: Shenandoah: gc/shenandoah/mxbeans tests should fail when no notifications arrive

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4611/files
  - new: https://git.openjdk.java.net/jdk/pull/4611/files/77278d43..a00be3e6

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4611&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4611&range=00-01

  Stats: 12199 lines in 357 files changed: 3981 ins; 7160 del; 1058 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4611.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4611/head:pull/4611

PR: https://git.openjdk.java.net/jdk/pull/4611