Unify the re-balancing logic for ec.encode with ec.balance. (#6339)

Among others, this enables recent changes related to topology aware
re-balancing at EC encoding time.

weed/shell/command_ec_rebuild.go

@@ -4,10 +4,10 @@ import (
 	"context"
 	"flag"
 	"fmt"
-	"github.com/seaweedfs/seaweedfs/weed/pb"
 	"io"
 
 	"github.com/seaweedfs/seaweedfs/weed/operation"
+	"github.com/seaweedfs/seaweedfs/weed/pb"
 	"github.com/seaweedfs/seaweedfs/weed/pb/volume_server_pb"
 	"github.com/seaweedfs/seaweedfs/weed/storage/erasure_coding"
 	"github.com/seaweedfs/seaweedfs/weed/storage/needle"
@@ -74,7 +74,7 @@ func (c *commandEcRebuild) Do(args []string, commandEnv *CommandEnv, writer io.W
 	}
 
 	// collect all ec nodes
-	allEcNodes, _, err := collectEcNodes(commandEnv, "")
+	allEcNodes, _, err := collectEcNodes(commandEnv)
 	if err != nil {
 		return err
 	}