clientv3: set current revision to create rev regardless of CreateNotify

Turns out the optimization to ignore setting the init rev for
current revision watches breaks some ordering assumptions. Since
Watch only returns a channel once it gets a response, it should
bind the revision at the time of the first create response.

Was causing TestWatchReconnInit to fail.

clientv3/watch.go

@@ -615,13 +615,18 @@ func (w *watchGrpcStream) serveSubstream(ws *watcherStream, resumec chan struct{
 					// send first creation event only if requested
 					if ws.initReq.createdNotify {
 						ws.outc <- *wr
-						if ws.initReq.rev == 0 {
-							// current revision of store; returning the
-							// create response binds the current revision to
-							// this revision, so restart with it if there's a
-							// disconnect before receiving any events.
-							nextRev = wr.Header.Revision
-						}
+					}
+					// once the watch channel is returned, a current revision
+					// watch must resume at the store revision. This is necessary
+					// for the following case to work as expected:
+					//	wch := m1.Watch("a")
+					//	m2.Put("a", "b")
+					//	<-wch
+					// If the revision is only bound on the first observed event,
+					// if wch is disconnected before the Put is issued, then reconnects
+					// after it is committed, it'll miss the Put.
+					if ws.initReq.rev == 0 {
+						nextRev = wr.Header.Revision
 					}
 				}
 			} else {