message: fix getPartsNum in AdHocSchemaManager
diff: @@ -98,6 +98,10 @@ public:
  void addFTClient(const nebula::meta::cpp2::FTClient& client);
  + StatusOr<int32_t> getPartsNum(GraphSpaceID) {
  + return 1;
  + }
  +
  protected:
  folly::RWSpinLock tagLock_;
  