RFR: Remove Shenandoah from TestSmallHeap jtreg test

[Roman Kennke]

The TestSmallHeap test is bogus for Shenandoah. It verfies if the final
max heap size is pagesize*heap_bytes_per_card. On a machine with 64K
page size, this fails, because it ends up with an expected heap size of
32MB. But Shenandoah doesn't care about cards, and thus leaves heap size
at 4MB (as passed in via -Xmx).

I propose to remove Shenandoah from that test as quick fix. We may want
to add a derived small-heap test to gc/shenandoah later.

http://cr.openjdk.java.net/~rkennke/testsmallheap/webrev.00/

Test: hotspot_gc_shenandoah
 (well, duh, w/o that test now. but does pass all those tests on my big
aarch64 box now).

Ok? Or other opinions?

Roman