Integration test for bulk load replication. Defines three clusters, with the following
replication topology: "1 <-> 2 <-> 3" (active-active between 1 and 2, and active-active between
2 and 3).
For each of defined test clusters, it performs a bulk load, asserting values on bulk loaded file
gets replicated to other two peers. Since we are doing 3 bulk loads, with the given replication
topology all these bulk loads should get replicated only once on each peer. To assert this,
this test defines a preBulkLoad coprocessor and adds it to all test table regions, on each of the
clusters. This CP counts the amount of times bulk load actually gets invoked, certifying
we are not entering the infinite loop condition addressed by HBASE-22380.