Fix a sync deadlock, and add a stress testing example app

[adamchel]

This PR fixes a deadlock that was caused by the DataSynchronizer waiting for a stream to finish opening while the stream was waiting for the DataSynchronizer to release a lock. These changes are quite small, and mostly in the core remote mongo service.

This PR also adds an example app that can serve as a tool for us to do manual stress testing.

[dkaminsky]

lgtm, though wondering if those non-concurrent HashMaps in the instance listener impl are going to be problematic at some point

[coveralls]

Coverage increased (+0.03%) to 66.86% when pulling 7ef6244 on adamchel:stress-testing into 5f88d96 on mongodb:master.