When connections are broken on Watch, write fewer errors to logs

Watch depends on long running connections, which intervening proxies
may break without the control of the remote server. Specific errors
handled are io.EOF, io.EOF wrapped by *url.Error, http connection
reset errors (caused by race conditions in golang http code), and
connection reset by peer (simply tolerated).

pkg/watch/watch.go

@@ -56,6 +56,26 @@ type Event struct {
 	Object runtime.Object
 }
 
+type emptyWatch chan Event
+
+// NewEmptyWatch returns a watch interface that returns no results and is closed.
+// May be used in certain error conditions where no information is available but
+// an error is not warranted.
+func NewEmptyWatch() Interface {
+	ch := make(chan Event)
+	close(ch)
+	return emptyWatch(ch)
+}
+
+// Stop implements Interface
+func (w emptyWatch) Stop() {
+}
+
+// ResultChan implements Interface
+func (w emptyWatch) ResultChan() <-chan Event {
+	return chan Event(w)
+}
+
 // FakeWatcher lets you test anything that consumes a watch.Interface; threadsafe.
 type FakeWatcher struct {
 	result  chan Event