etcdhttp, v2http, etcdserver: use etcdserver.{Server,ServerV2} interfaces

etcdserver/api/cluster.go

@@ -33,9 +33,6 @@ type Cluster interface {
 	// Member retrieves a particular member based on ID, or nil if the
 	// member does not exist in the cluster
 	Member(id types.ID) *membership.Member
-	// IsIDRemoved checks whether the given ID has been removed from this
-	// cluster at some point in the past
-	IsIDRemoved(id types.ID) bool
 	// Version is the cluster-wide minimum major.minor version.
 	Version() *semver.Version
 }