user-group: Add chdir("/") after chroot()
user-group: Add chdir("/") after chroot()

rpmlint finds this:
`E: missing-call-to-chdir-with-chroot /usr/bin/ignition`
and in our case I don't think it'll matter as nothing is reading
from the current working directory, but it's definitely best
practice.

(Although I would say this code should be replaced by
 forking a container process off in the target (e.g. via bwrap)
 and talking to it over IPC)

ajeddeloh/ignition,coreos/ignition,ajeddeloh/ignition,coreos/ignition,coreos/ignition,ajeddeloh/ignition