KUDU-1097: turn on 3-4-3 replica management scheme
KUDU-1097: turn on 3-4-3 replica management scheme

This patch enables 3-4-3 replica management scheme for tablets: now
the 3-4-3 scheme is used by default.  To switch back to 3-2-3 scheme,
set --raft_prepare_replacement_before_eviction=false for both masters
and tablet servers.

Change-Id: I781d02fe455140ed3a4693438eece74f07700946
Reviewed-on: http://gerrit.cloudera.org:8080/8862
Tested-by: Kudu Jenkins
Reviewed-by: Mike Percy <e07a1fd797b473a9c849e618aa2ce06d8055760b@apache.org>

cloudera/kudu,andrwng/kudu,andrwng/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,cloudera/kudu,EvilMcJerkface/kudu,cloudera/kudu,helifu/kudu,cloudera/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,cloudera/kudu,helifu/kudu,andrwng/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,helifu/kudu,andrwng/kudu,cloudera/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,cloudera/kudu,InspurUSA/kudu,EvilMcJerkface/kudu,helifu/kudu,andrwng/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,andrwng/kudu,andrwng/kudu,helifu/kudu,InspurUSA/kudu,cloudera/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,andrwng/kudu,cloudera/kudu,helifu/kudu,andrwng/kudu