To manually finish an upgrade and continue rebooting nodes that were not rebooted, complete the following steps:
# show slot detail | include "information|Image|State|ver:"
Slot-1 information:
     State:               Operational
     Current State:       MASTER
     Image Selected:      primary
     Image Booted:        secondary
     Primary ver:         31.3.1.22
     Secondary ver:       31.3.0.106
Slot-2 information:
     State:               Operational
     Current State:       BACKUP (In Sync)
     Image Selected:      primary
     Image Booted:        secondary
     Primary ver:         31.3.1.22
     Secondary ver:       31.3.0.106
Slot-3 information:
     State:               Operational
     Current State:       STANDBY
     Image Selected:      primary
     Image Booted:        primary
     Primary ver:         31.3.1.22
     Secondary ver:       31.3.0.106
Slot-4 information:
     State:               Operational
     Current State:       STANDBY
     Image Selected:      primary
     Image Booted:        secondary
     Primary ver:         31.3.1.22
     Secondary ver:       31.3.0.106

Note
After each reboot, allow a few minutes for the network to converge before proceeding.