RFR: Test fixes, pack of 3

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/tests-3-pack/webrev.01/

Please review this pack of test fixes (to be pushed as separate changesets), which include:

*) "TestHeapDump should unlock aggressive heuristics"

Obvious one, need to unlock "aggressive" for release builds.

*) "Make sure -XX:+ShenandoahVerify comes first in the tests"

This is a convenience change: jtreg would stop executing tests configuration on first failure, so it
is better if it fails with Verifier and nice message, and not cryptically. This means Verifier
configurations should come first in config list

*) "Add -XX:+ShenandoahVerify to more interesting tests"

Adds more verification in tests that actually mess with the heap.

Testing: hotspot_gc_shenandoah {fastdebug|release}

Thanks,
-Aleksey