* Fix CONFIG_DB_INITIALIZED flag check logic and set/reset flag for warm-reboot
* Fix db-cli usage
* Handle same image warm-reboot and generalize handling of INIT flag
* Cover boot from ONIE case: set config init flag when minigraph, config_db are missing
* Handle case: first boot of SONiC
* Check for config init flag
* Simplify logic, and do not call db_migrator for same image reboot