'update_reboot' is undefined

[robertdebock]

Describe the bug

fatal: [HOST]: FAILED! => {"msg": "The conditional check 'update_reboot' failed. The error was: error while evaluating conditional (update_reboot): 'update_reboot' is undefined\n\nThe error appears to have been in 'roles/robertdebock.common/handlers/main.yml': line 7, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- name: reboot for hostname\n  ^ here\n"}

Copy-pasted from the update role, needs a fix.

To Reproduce
Steps to reproduce the behavior:

1. Run this role.
2. See error.