Add tree rebuild in 2i AAE test

This helps verify the problem where 2i AAE trees got dropped during a
rebuild, breaking future runs of the repair-2i command.
Enhanced the wait for AAE trees function to try a lock on the built
trees. The building process may have notified its end, but it is still
possible to get a not_built if you try to get a lock very quickly. This
attempts the lock for each partition before declaring total victory.
Merge branch 'bugfix/2i-aae-tree-rebuild' into riak/1.4

Conflicts:
	src/rt.erl