8185273: Test8004741.java crashes with SIGSEGV in JDK10-hs nightly
Summary: Threads::parallel_java_threads_do() needs to call VMThread::claim_oops_do() to avoid causing a parallel GC to miss the VMThread.
Reviewed-by: shade, rkennke, kvn, gthornbr
8183973: gc/TestFullGCALot.java fails in JDK10-hs nightly
Summary: Provide extra NewSize to avoid failure in running test with UseDeterministicG1GC option.
Reviewed-by: mgerdin, eosterlund