tests are using too much memory

[Bruce Schuchardt]

The single-threaded gradle build is now using xmx3g but when tests start 
running it's consuming over 4gb.  I also have Intellij and Chrome 
running on my 16gb laptop and the tests are causing me to run out of 
RAM.  It's set to use 1/2 of the CPUs on a machine but I am finding that 
all of my CPUS are pegged.

Can we change this behavior to only run tests in parallel if "-parallel" 
has been specified, or ramp it down to 1/4 of the CPUs?