[Enhancement] disable FE scale to 1

[yandongxiao]

If scale to 1, Operator will report an error.

k get starrocksclusters.starrocks.com kube-starrocks
NAME             PHASE    FESTATUS   BESTATUS   CNSTATUS   FEPROXYSTATUS
kube-starrocks   failed   running               running

k get starrocksclusters.starrocks.com kube-starrocks -oyaml | grep reason
reason: 'error from FE controller: the replicas of statefulset kube-starrocks-fe can not be scaled to 1'

[brucejrc]

fe number set from five to two, fe will run no leader?

[yandongxiao]

StarRocks uses BDBJE to select leader for FE, and I did not test this case.
I think you'd better to scale FE one by one.