replicate global zone /etc/default/init in new zones

[citrus-it]

This change is a quick update to address #4 - fixes #4
The differing timezones between the GZ and an NGZ caused confusion during a recent debugging session.

This isn't the approach suggested in #4, instead we just copy the GZ's init file into the new zone after extracting the baseline archive, so that a new zone's timezone and umask match the GZ at the time of creation.

gimlet-sn06 # testzone
test: No such zone configured
Use 'create' to begin configuring a new zone.
A ZFS file system has been created for this zone.
INFO: omicron: installing zone test @ "/zones/test"...
INFO: omicron: replicating /usr tree...
INFO: omicron: replicating /lib tree...
INFO: omicron: replicating /sbin tree...
INFO: omicron: pruning SMF manifests...
INFO: omicron: pruning global-only files...
INFO: omicron: unpacking baseline archive...
INFO: omicron: copying /etc/default/init...
INFO: omicron: install complete, probably!
gimlet-sn06 # cat /zones/test/root/etc/default/init
#
# This file is /etc/default/init.
# This file looks like a shell script, but it is not.
#
# Lines of this file should be of the form VAR=value, where VAR is one of
# TZ, LANG, CMASK, or any of the LC_* environment variables.  value may
# be enclosed in double quotes (") or single quotes (').
#
TZ=UTC
CMASK=022

[jclulow]

I think this is more brittle than just including a static copy of the file we want at build time, but I also cannot immediately conceive of (for this file, at least) a way this is likely to go particularly wrong: if the TZ is anything other than UTC in the global zone, the sled is already demonstrably broken.

So, while I would prefer the static file, you're welcome to go ahead!