Currently in production instances of Elasticsearch we set a couple of
system properties by default. We currently do not apply all of these
system properties in tests. This commit applies these properties in the
tests. Additionally it enables the unpooled allocator about 1/4 of the
time, the pooled allocator with direct buffer pooling about 1/4 of the
time, and the pooled allocator without direct buffer pooling about 1/2
of the time.