* backport new platform api to 201811, reboot cause part
* install new platform api on host
* 1. remove chassis's dependency on sonic_platform_daemon.
2. add some mellanox-specific hardware reboot causes.
3. fix typo in files/image_config/process-reboot-cause/process-reboot-cause.
* 1. add dependency of sonic_platform for base image
2. handle the case of reboot cause file not found
* adjust log message.
In case of going from previous iteration of SONiC, and the last reboot
was hardware, REBOOT_CAUSE_FILE may not be present and the service may
throw an error.
