Make test computations explicit

This test is full of magic numbers, making it very difficult to fix when
the underlying code changes. There are some obvious errors, such as an
instance having a different memory_mb value than its flavor. This patch
attempts to sort these issues out, making it easier to work on the
resource tracker with confidence.

Change-Id: I4549f0d9b10a5ac65f169199b98b8975ef2a8cd3
Merge "Make test computations explicit"