clientv3/integration: add TestBalancerUnderNetworkPartitionWatch
clientv3/integration: add TestBalancerUnderNetworkPartitionWatch

Signed-off-by: Gyu-Ho Lee <3454051ee3341eb69bdf6fca40899cdad4d86496@gmail.com>

cockroachdb/etcd,bdarnell/etcd,mkumatag/etcd,ajityagaty/etcd,etcd-io/etcd,rnaveiras/etcd,mqliang/etcd,whuwxl/etcd,coreos/etcd,heyitsanthony/etcd,dannysauer/etcd,dannysauer/etcd,sebrandon1/etcd,sinsharat/etcd,vimalk78/etcd,li-ang/etcd,etcd-io/etcd,xiang90/etcd,xiang90/etcd,fanminshi/etcd,whuwxl/etcd,mqliang/etcd,cockroachdb/etcd,akauppi/etcd,bluebreezecf/etcd,mqliang/etcd,lorneli/etcd,vimalk78/etcd,rnaveiras/etcd,rnaveiras/etcd,sebrandon1/etcd,gyuho/etcd,glevand/coreos--etcd,fanminshi/etcd,ajityagaty/etcd,etcd-io/etcd,akauppi/etcd,heyitsanthony/etcd,bluebreezecf/etcd,coreos/etcd,li-ang/etcd,mkumatag/etcd,gyuho/etcd,mkumatag/etcd,sinsharat/etcd,joshix/etcd,glevand/coreos--etcd,joshix/etcd,lorneli/etcd,ajityagaty/etcd,bdarnell/etcd