Switch 10gen/mongo unit tests over to running on EngFlow's remote cluster with remote build execution. This is a spike and may not land on master depending on the performance. The cost savings here will only be moderate since it's only reducing a percentage of ELB traffic. I would expect at best a $5k/month cost savings when/if this lands.

This is being prioritized for the purpose of de-risking remote execution as a cost savings measure. Once the unit tests are runnable with remote build execution, I'm going to kick off a large series of them during the night so we can measure ELB cost and compare it with unit tests running without RBE.