The changes from SERVER-26827 made it possible to run tests on the ARM machines typically used for compiling the server. There is a known performance issue with the ubuntu1604-arm64-1.linaro.build.10gen.cc host related to it using spinning HDDs. We should stop running the concurrency suite on the ubuntu1604-arm64-large distro until the underlying issue can be addressed in order to avoid triggering task timeouts from the machine making slow progress.