Remove confusing log messages in serving graph rebuild.

These were logged originally to verify that contention was rare.
If it turned out to be common in practice, we should go back to
pessimistic locking.

Contention on the serving graph has indeed been rare, but when it does
happen, these messages are confusing because they seem to indicate a
problem.

go/vt/topotools/rebuild_shard.go

@@ -104,7 +104,7 @@ func rebuildCellSrvShard(ctx context.Context, log logutil.Logger, ts topo.Server
 			}
 			entry, err := topo.TabletEndPoint(tablet.Tablet)
 			if err != nil {
-				log.Warningf("EndPointForTablet failed for tablet %v: %v", tablet.Alias, err)
+				log.Warningf("TabletEndPoint failed for tablet %v: %v", tablet.Alias, err)
 				continue
 			}
 			endpoints.Entries = append(endpoints.Entries, entry)
@@ -127,7 +127,6 @@ func rebuildCellSrvShard(ctx context.Context, log logutil.Logger, ts topo.Server
 					// This type didn't exist when we first checked.
 					// Try to create, but only if it still doesn't exist.
 					if err := ts.CreateEndPoints(ctx, cell, si.Keyspace(), si.ShardName(), tabletType, endpoints); err != nil {
-						log.Warningf("CreateEndPoints(%v, %v, %v) failed during rebuild: %v", cell, si, tabletType, err)
 						switch err {
 						case topo.ErrNodeExists:
 							retryErrs.RecordError(err)
@@ -140,7 +139,6 @@ func rebuildCellSrvShard(ctx context.Context, log logutil.Logger, ts topo.Server
 
 				// Update only if the version matches.
 				if err := ts.UpdateEndPoints(ctx, cell, si.Keyspace(), si.ShardName(), tabletType, endpoints, version); err != nil {
-					log.Warningf("UpdateEndPoints(%v, %v, %v) failed during rebuild: %v", cell, si, tabletType, err)
 					switch err {
 					case topo.ErrBadVersion, topo.ErrNoNode:
 						retryErrs.RecordError(err)
@@ -157,9 +155,7 @@ func rebuildCellSrvShard(ctx context.Context, log logutil.Logger, ts topo.Server
 				wg.Add(1)
 				go func(tabletType topodatapb.TabletType, version int64) {
 					defer wg.Done()
-					log.Infof("removing stale db type from serving graph: %v", tabletType)
 					if err := ts.DeleteEndPoints(ctx, cell, si.Keyspace(), si.ShardName(), tabletType, version); err != nil && err != topo.ErrNoNode {
-						log.Warningf("DeleteEndPoints(%v, %v, %v) failed during rebuild: %v", cell, si, tabletType, err)
 						switch err {
 						case topo.ErrNoNode:
 							// Someone else deleted it, which is fine.