clientv3/integration: remove client keepalive in network partition tests
clientv3/integration: remove client keepalive in network partition tests

Those tests are about balancer endpoint switch, not about keepalive pings.

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

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