raft: make JoinAndStart more readable
raft: make JoinAndStart more readable

Signed-off-by: Alexander Morozov <2043cda4df124b840b98ee1c4307c199042efdf7@gmail.com>

deljuven/swarmkit,alyyousuf7/swarmkit,AliyunContainerService/swarmkit,elifa/swarmkit,sungwonh/swarmkit,fate-grand-order/swarmkit,yongtang/swarmkit,deljuven/swarmkit,fate-grand-order/swarmkit,dperny/swarmkit-1,docker/swarmkit,elifa/swarmkit,allencloud/swarmkit,docker/swarmkit,Noyan759/swarmkit,diogomonica/swarmkit,AliyunContainerService/swarmkit,allencloud/swarmkit,aaronlehmann/swarmkit,cheyang/swarmkit,alyyousuf7/swarmkit,RenaudWasTaken/swarmkit,jlhawn/swarmkit,aaronlehmann/swarmkit,diogomonica/swarmkit,sungwonh/swarmkit,Noyan759/swarmkit,RenaudWasTaken/swarmkit,dperny/swarmkit-1,yongtang/swarmkit,jlhawn/swarmkit,cheyang/swarmkit