NEWS: update v3.1.6
NEWS: update v3.1.6

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

mickep76/etcd,xiang90/etcd,ajityagaty/etcd,whuwxl/etcd,heyitsanthony/etcd,armstrongli/etcd,rnaveiras/etcd,visheshnp/etcd,fanminshi/etcd,a-robinson/etcd,coreos/etcd,coreos/etcd,mkumatag/etcd,sinsharat/etcd,bluebreezecf/etcd,dannysauer/etcd,mkumatag/etcd,fanminshi/etcd,visheshnp/etcd,etcd-io/etcd,akauppi/etcd,mickep76/etcd,a-robinson/etcd,mqliang/etcd,YuleiXiao/etcd,ajityagaty/etcd,li-ang/etcd,sebrandon1/etcd,mqliang/etcd,sebrandon1/etcd,armstrongli/etcd,YuleiXiao/etcd,cockroachdb/etcd,vimalk78/etcd,glevand/coreos--etcd,ajityagaty/etcd,plasticbox/etcd,glevand/coreos--etcd,xiang90/etcd,sinsharat/etcd,yudai/etcd,heyitsanthony/etcd,bdarnell/etcd,cockroachdb/etcd,yudai/etcd,mqliang/etcd,joshix/etcd,lorneli/etcd,dannysauer/etcd,whuwxl/etcd,etcd-io/etcd,mkumatag/etcd,plasticbox/etcd,li-ang/etcd,lorneli/etcd,etcd-io/etcd,bdarnell/etcd,rnaveiras/etcd,gyuho/etcd,bluebreezecf/etcd,vimalk78/etcd,akauppi/etcd,joshix/etcd,rnaveiras/etcd,gyuho/etcd