RFR 8215299: Remove G1CMTask::should_exit_termination()'s undesirable side-effect

[Kim Barrett]

> On Jan 9, 2019, at 8:28 AM, zgu at redhat.com wrote:
> 
> Ping! Could I have reviews for this RFR?
> 
> New webrev updated copyright year:
> http://cr.openjdk.java.net/~zgu/JDK-8215299/webrev.01/
> 
> It also passed submit tests.

Looks good, but I’d like to see more testing of something this “core”, especially a bit of stress testing.
The submit tests are more at the level of “smoke” tests.

Given that most callers of regular_clock_call now conditionally call
set_has_aborted, a helper function to encapsulate that might be nice.