Update mongodb to 2.6.3

2.6.3 - June 19, 2014
- Equality queries on _id with projection may return no results on sharded
  collections
- Equality queries on _id with projection on _id may return orphan documents
  on sharded collections

2.6.2 - June 16, 2014
- Query plans with differing performance can tie during plan ranking
- mongod may terminate if x.509 authentication certificate is invalid
- Temporary map/reduce collections are incorrectly replicated to secondaries
- mongos incorrectly targets multiple shards for nested field shard key
  predicates
- rs.stepDown() during mapReduce causes fassert when writing to op log