Improve identification of a controller system

Instead of looking for whether a srv-gnome-hwtest partition exists
(which prevents booting a controller system from USB to reinstall
it), look at the label of the root device.

This will prevent running the hwtest image as a controller by adding
a srv-gnome-hwtest partition, but we no longer need this mode of
operation.
gnome-hwtest-install: do basic setup of /srv/gnome-hwtest

Create the directory, initialize the repo, and create a stub
controller.conf.
Add a --simulator option to gnome-hwtest-install

--simulator can be combined with --controller to do the
initial setup for a controller system running under
gnome-hwtest-simulator.

Remove the obsolete gnome-hwtest-initialize-repo script.
Fix up for the removal of the current symlink in OSTree

Use ostree admin --print-current-dir instead of looking for a current/
symlink to find the current deployment directory.

Use ostree admin instutil set-kargs rather than redeploying (which
required figuring out the current checksum)
Upload an error report on failure

If an update or test job fails, upload an error report to perf.gnome.org,
including the syslog exported from the test machine.