Retry writes to mongo on AutoReconnect

When pymongo raises an AutoReconnect exception we should attempt the
write again.

http://api.mongodb.org/python/2.5/examples/high_availability.html#high-availability-and-mongos

Ulatimately we should consider moving over to a MongoReplicaSetClient

http://api.mongodb.org/python/2.5/examples/high_availability.html#mongoreplicasetclient