RFR: Disable suspendible workers (again)

[Aleksey Shipilev]

On 10/18/2018 11:35 AM, Roman Kennke wrote:
> I recently enabled suspendible workers because I suspected running
> workers would conflict with deoptimization. This has proved wrong, and I
> would like to disable it (by default) again. We shall leave it in
> though, as kind of red button, in case anybody ever encounters a problem
> with GC workers during non-GC-safepoints. In order to avoid bitrotting
> this code, I added a few tests to run with +STS
> 
> Testing: tier3_gc_shenandoah
> 
> http://cr.openjdk.java.net/~rkennke/disable-sts/webrev.00/

Looks good.

-Aleksey