First boot asks again for a refused user name, and a second apply is told to reboot

[DevomB]

Two prompts sent a user the wrong way.

• First boot. A user name the setup refused (a capital letter is enough) ended the setup: the machine went on to a login prompt with no account, and only the next boot asked again. new_user now says why the name was refused and asks again, three times at most, as the password question does; after that, or with no answer in ten minutes, the next boot asks. tools/tests/firstboot.sh drives it with a stand-in useradd: a plain name, a refused name then a good one, three refused names, and no answer.
• A second apply. While a trial is armed and not yet booted, kryptik-update apply said "reboot first, or run rollback". Rollback arms the other slot, which is the slot just armed, so the trial stays and apply still refuses. The message says to reboot.

firstboot.sh is an input of stage 04's services step and kryptik-update of updater: both are in the stage's tail, so no package is built again.