PdOracle leak if other error happens in NewKVStore

[lance6716]

client-go/tikv/kv.go

Lines 319 to 326 in 0fdd255

	func NewKVStore(uuid string, pdClient pd.Client, spkv SafePointKV, tikvclient Client, opt ...Option) (*KVStore, error) {
	o, err := oracles.NewPdOracle(pdClient, &oracles.PDOracleOptions{
	UpdateInterval: defaultOracleUpdateInterval,
	})
	if err != nil {
	return nil, err
	}
	ctx, cancel := context.WithCancel(context.Background())

forget to call o.Close and other objects' Close. It will cause some error log like [pd.go:474] ["updateTS error"] and [region_cache.go:763] ["refresh full store list failed"]