Running the test suite can hog the system

[vemv]

I tried running the test suite. Some tests run fine, if just a little slow.

But I couldn't complete running the test suite since all my 16 cores started getting hogged.

Thankfully I had Yourkit running so I could see there were many threads like these actively doing work:

The total active thread count was around 4000 which is far from normal. Probably there's a leak of some sort.

Here's a (unusually humonguous) thread dump: https://gist.githubusercontent.com/vemv/2b0011329ce8f40fe04764784f314586/raw/772ba1799b53556e686611d417d721dfeceb779a/gistfile1.txt