We'd like to be able to test distributed-lock takeover scenarios. Right now, though, the lock timeouts are set to 15 minutes, which prevents effective testing:

https://github.com/mongodb/mongo/blob/r3.1.7/src/mongo/s/catalog/legacy/distlock.h#L43
https://github.com/mongodb/mongo/blob/r3.1.7/src/mongo/s/catalog/replset/replset_dist_lock_manager.cpp#L57

Let's make the timeouts configurable with either:

1. MONGO_EXPORT_SERVER_PARAMETER macros
2. Configurable failpoints