Log Message:
Update mongodb to 2.6.9.

2.6.9 - March 24, 2015
- Resolve connection handling related crash with mongos instances
- Add server parameter to configure idle cursor timeout
- Remove duplicated (orphan) documents from aggregation pipelines with
  _id queries in sharded clusters
- Fixed crash in geoNear queries with multiple 2dsphere indexes

2.6.8 - February 25, 2015
- Add listCollections command functionality to 2.6 shell and client
- copydb/clone commands can crash the server if a primary steps down
- Secondary fasserts trying to replicate an index
- Query optimizer should always use equality predicate over unique
  index when possible