GitLab

Fix two issues:
1. Rdb_ddl_manager::rename() loses the value of m_hidden_pk_val. new
object used to get 0, which means "not loaded from the db yet".

2. ha_rocksdb::load_hidden_pk_value() uses current transaction (and its
snapshot) when loading hidden PK value from disk. This may cause it to
load an out-of-date value.