RFR [11u]: Bulk backports to sh/jdk11

[Roman Kennke]

Yeah looks good! Thanks!

Roman


> Let's pick up a few easy backports to sh/jdk11:
>   [backport] 8222125: Shenandoah: Crash when running with ShenandoahParallelSafepointThreads=1
>   [backport] 8222130: Shenandoah should verify roots after pre-evacuation
>   [backport] 8222185: Shenandoah should report "committed" as capacity
>   [backport] 8222186: Shenandoah should not uncommit below minimum heap size
>   [backport] 8221735: Shenandoah fails ctw/modules/jdk_management_agent.java with Traversal
>   [backport] 8215356: Disable x86_32 Shenandoah build to avoid hotspot/tier1 failures
> 
> Webrev:
>    http://cr.openjdk.java.net/~shade/shenandoah/backports/jdk11-20190424/webrev.01/
> 
> Testing: hotspot_gc_shenandoah {fastdebug,release}
>