test: Add fstab to all ufs images

Ensure that we populate /etc/fstab for all the ufs images. Tweak sizes
while I'm at it.

Note: This file could use a good refactoring... or maybe a rewrite in
python or lua.

Sponsored by: Netflix
Reviewed by: tsoome
Differential Revision: https://reviews.freebsd.org/D38317

stand: Add testing for i386 as well to full-test.sh

Sponsored by: Netflix

testing: Make sure to specify a name for zpools

Zpools have to have a name. Pools created w/o a name aren't legit and
trigger a number of bugs.

Sponsored by: Netflix

full-test: Start of a full testing suite.

full-test.sh aims to be a test suite generator for the boot loader. It
tries to grab artifacts from the web and then constructs minimal boot
environments from that as well as writing qemu-system-* using scripts
that facilitates testing all the ways we can boot... At least all the
ways that we an boot that qemu can emulate.

This is very much a work in progress, and likely could use a good
cleanup at some point.

Sponsored by: Netflix