It was previously possible for the 'minority' network partition to
become the majority network partition by a naive network partitioning
strategy. Previously, when a preference list of 5 keyspace partitions
was created on only four distinct nodes, it became possible for a 2 node
'minority' network partition group to actually have a majority of
keyspace partitions because 2 keyspace partitions were assigned to 1
node in the 'minority' group. This was fixed so that the 'majority'
group now always has a majority of keyspace partitions by preventing
nodes with greater than 1 keyspace partition from becoming part of the
'minority' group.
Add ensemble_basic4, ensemble_sync, and ensemble_interleave tests.
ensemble_sync tests the new AAE-based peer syncing logic. The test
checks various scenarios with different levels of data corruption.
ensemble_interleave tests a specific scenario where two peers become
corrupted one after the other. This tests the scenario where the
second peer becomes untrusted while the first peer may be syncing
with it.
