bug report: create more than 1 klusterlet for same managed cluster

[ycyaoxdu]

There is no check in code logic for whether klusterlet is already installed. If we run join command more than once, more than one klusterlet would be created.

╰─# k get klusterlets                                                                                                              1 ↵
NAME                       AGE
klusterlet-hosted-0uo3ag   17h
klusterlet-hosted-82mi7k   92m
klusterlet-hosted-g08drc   93m

reported by @zhujian7

[ycyaoxdu]

/kind bug