Remove old TODO

There is nothing to be done for this TODO, removed it.
Use consistent naming for the anti entropy tick

Use the same name and timeout as KV to be consistent.
Mark index hashtree as built immediately

When possible, mark the index hashtree as built immediately. This allows
exchange to be performed earlier. It is useful when standing up new
nodes which don't have any data yet and you don't want to wait for the
AAE manager to build all partitions.
Merge pull request #301 from basho/feature/rz/aae-built-immediately

Mark AAE trees as built immediately