internal/resolver: fix possible goroutine leak in TestSafeConfigSelector (#5058)
internal/resolver: fix possible goroutine leak in TestSafeConfigSelector (#5058)


dfawley/grpc-go,grpc/grpc-go,stanley-cheung/grpc-go,grpc/grpc-go,stanley-cheung/grpc-go,menghanl/grpc-go,dfawley/grpc-go,menghanl/grpc-go