Temporary: Shutdown our VMs after provisioning

While we do recommend a reboot, just preemptively shutdown all of
our VMs after provisioning to ensure anything that follows (e.g. CI
runs) will be from a cleaner state.

We tried to implement this in workstation-ci itself (<freedomofpress/securedrop-workstation-ci#44>),
but it isn't working as we desired, so we'll do this for now and revert
once CI is fixed.

files/provision-all

@@ -47,3 +47,8 @@ qvm-check --quiet sd-fedora-39-dvm 2> /dev/null && \
   sudo qubesctl --show-output --skip-dom0 --targets sd-fedora-39-dvm state.highstate && \
   qvm-shutdown --wait sys-usb && qvm-start sys-usb || \
   sudo qubesctl --show-output --skip-dom0 --targets sys-usb state.highstate
+
+# Shut down all VMs to ensure new configuration takes place, if the user doesn't reboot.
+echo "will shut down the following VMs"
+qvm-ls --tags sd-workstation
+qvm-ls --tags sd-workstation --raw-list | xargs qvm-shutdown --wait