1. on receiving a CCM_TYPE_LEAVE message, if we are the only node left, we can go to CCM_STATE_JOINED state directly This applies to all states in ccm (TBD)
2. ccm membership structs are over-complicated, e.g., these structs are used to store membership info (a) llm_info_t which represents low leverl membership. This struct stores all nodes information.
(b) ccm_info_t which is a struct that stores most of the global information. ccm_member[MAXNODE] is used to store the current membership, each one indicates the index to llm_info_t::nodes