switch-to-configuration: Use systemctl's --no-legend flag

(cherry picked from commit 37e6e08cdee082d9f60ab2900c960f2f594933a0)
switch-to-configuration: Use old systemctl to stop units

Otherwise, when switching from systemd 203 to 212, you get errors like:

  Failed to stop remote-fs.target: Bad message
  Failed to stop systemd-udevd-control.socket: Bad message
  ...

(cherry picked from commit 56b4b841ae45c9fb512096852d06410e7ebe45d2)