Disable the watch cache for most resources by default

Any resource named by the heuristics gets a watch cache by default.
Admins can restore the previous behavior by setting
`--default-watch-cache-size` to a positive integer. This reduces the
amount of total memory allocated on large cluster significantly at minor
cost in CPU on the etcd process and an increase in network bandwidth to
etcd.

pkg/cmd/server/kubernetes/master/master_config.go

@@ -150,7 +150,7 @@ func BuildKubeAPIserverOptions(masterConfig configapi.MasterConfig) (*kapiserver
 	server.Etcd.StorageConfig.KeyFile = masterConfig.EtcdClientInfo.ClientCert.KeyFile
 	server.Etcd.StorageConfig.CertFile = masterConfig.EtcdClientInfo.ClientCert.CertFile
 	server.Etcd.StorageConfig.CAFile = masterConfig.EtcdClientInfo.CA
-	server.Etcd.DefaultWatchCacheSize = DefaultWatchCacheSize
+	server.Etcd.DefaultWatchCacheSize = 0
 
 	server.GenericServerRunOptions.CorsAllowedOriginList = masterConfig.CORSAllowedOrigins
 	server.GenericServerRunOptions.MaxRequestsInFlight = masterConfig.ServingInfo.MaxRequestsInFlight