recovery: report compliant reboot reason (Part Deux)

shutdown and reboot should have a corresponding sub-reason.

Updating:
    "reboot,userrequested,fastboot"
    "reboot,userrequested,recovery"
    "reboot,userrequested,recovery,ui"
    "shutdown,userrequested,fastboot"
    "shutdown,userrequested,recovery"
    "reboot,unknown#" (Can't happen, debug)

Test: none
Bug: 133326470
Change-Id: Icf1ab0d462ec2de2272914a36994a095998d6186