Fix flaky raft test
Fix flaky raft test

Change TestRaftLeaderLeave to check the new leader after the first
leader leaves, instead of assuming that node 2 is the new leader.

Increase the sleep for leader failover to 6 seconds, since apparently 4
is not enough. The sleeps will be replaced with proper monitoring soon.

Signed-off-by: Aaron Lehmann <8ecfc6017a87905413dcd7d63696a2a4c351b604@docker.com>

elifa/swarmkit,Noyan759/swarmkit,diogomonica/swarmkit,cheyang/swarmkit,allencloud/swarmkit,fate-grand-order/swarmkit,cheyang/swarmkit,yp-engineering/swarmkit,docker/swarmkit,cezarsa/swarmkit,runshenzhu/swarmkit,AliyunContainerService/swarmkit,jlhawn/swarmkit,Noyan759/swarmkit,yp-engineering/swarmkit,dperny/swarmkit-1,sungwonh/swarmkit,aaronlehmann/swarmkit,AliyunContainerService/swarmkit,yongtang/swarmkit,vasil-yordanov/swarmkit,dperny/swarmkit-1,alyyousuf7/swarmkit,diogomonica/swarmkit,runshenzhu/swarmkit,vasil-yordanov/swarmkit,yongtang/swarmkit,deljuven/swarmkit,fate-grand-order/swarmkit,jlhawn/swarmkit,deljuven/swarmkit,sungwonh/swarmkit,RenaudWasTaken/swarmkit,aaronlehmann/swarmkit,RenaudWasTaken/swarmkit,cezarsa/swarmkit,allencloud/swarmkit,elifa/swarmkit,alyyousuf7/swarmkit,docker/swarmkit