Buck defaults to running 1.25 * ncpus tests in parallel. If each test
uses a heap size of 128M then an 8 core system will need at least
1.25G of RAM for JVM heap during test execution. The actual memory
used will of course be much higher due to JVM overhead.
Set a default memory for acceptance tests to prevent a huge explosion
during `buck test --all`.
Change-Id: I373df822c029d2dc24c625129f540211cda910e7
79c58714de