[Bug] namespace can not set multiple clusters at the same time

[zymap]

(⎈ |yong-offload-perf:pulsar-offload)➜  apache-zookeeper-3.5.7-bin pulsarctl1 namespaces get-clusters public/default
[
  "standalone-1"
]
(⎈ |yong-offload-perf:pulsar-offload)➜  apache-zookeeper-3.5.7-bin pulsarctl1 namespaces set-clusters public/default -c standalone-1
-c standalone-2
Set replication clusters successfully for public/default
(⎈ |yong-offload-perf:pulsar-offload)➜  apache-zookeeper-3.5.7-bin pulsarctl1 topics internal-stats migration
[✖]  code: 412 reason: Namespace missing local cluster name in clusters list: local_cluster=standalone-1 ns=public/default clusters=[standalone-2]
(⎈ |yong-offload-perf:pulsar-offload)➜  apache-zookeeper-3.5.7-bin pulsarctl1 namespaces get-clusters public/default
[
  "standalone-2"
]
(⎈ |yong-offload-perf:pulsar-offload)➜  apache-zookeeper-3.5.7-bin pulsarctl1 namespaces set-clusters public/default -c standalone-1 -c standalone-2
Set replication clusters successfully for public/default
(⎈ |yong-offload-perf:pulsar-offload)➜  apache-zookeeper-3.5.7-bin pulsarctl1 namespaces get-clusters public/default
[
  "standalone-2"
]

[nodece]

Correct command: pulsarctl1 namespaces set-clusters public/default -c standalone-1,standalone-2.