RFR: 8289003: JavaThread::check_is_terminated() implementation should rely on Thread-SMR [v2]

[Daniel D. Daugherty]

> A small fix to change `JavaThread::check_is_terminated()` to rely on Thread-SMR.
> The change is textually trivial, but requires a bit of thinking about the JavaThread
> lifecycle. Since this is a cleanup of some old Thread-SMR related changes, I also
> took the time to cleanup some comments and white space while I was visiting the
> uses of `_vm_exited`.
> 
> Mach5 Tier1 has no related failures. Mach5 Tier[23] testing has just started.

Daniel D. Daugherty has updated the pull request incrementally with one additional commit since the last revision:

  dholmes CR - fix typo in comment.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9502/files
  - new: https://git.openjdk.org/jdk/pull/9502/files/baf43a88..67b19cf5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9502&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9502&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9502.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9502/head:pull/9502

PR: https://git.openjdk.org/jdk/pull/9502