RFR: Shenandoah filter for vmTestbase/nsk/jvmti/scenarios/general_functions/GF08/gf08t001

[Zhengyu Gu]

Webrev: 
http://cr.openjdk.java.net/~zgu/shenandoah/sh_concgc_gf08t001/webrev.00/

Shenandoah supports explicit invocation of concurrent GC, but not Graal, 
so handles it accordingly.

Test:

vmTestbase/nsk/jvmti/scenarios/general_functions/GF08/gf08t001/TestDriver.java

(fastdebug and release)


Thanks,

-Zhengyu