Use ConditionUser=1000 instead of manually testing the output of `id -u'.

The ConditionUser= directive was added in systemd v234, that's not in Stretch.

config/chroot_local-includes/usr/lib/systemd/user/tails-add-GNOME-bookmarks.service

 [Unit]
 Description=Add GTK bookmarks to some directories
 Documentation=https://tails.boum.org/contribute/design/application_isolation/
+ConditionUser=1000
 
 [Service]
 Type=oneshot

config/chroot_local-includes/usr/lib/systemd/user/tails-create-tor-browser-directories.service

 [Unit]
 Description=Create the Tor Browser amnesiac and persistent directories
 Documentation=https://tails.boum.org/contribute/design/application_isolation/
+ConditionUser=1000
 
 [Service]
 Type=oneshot

config/chroot_local-includes/usr/lib/systemd/user/tails-wait-until-tor-has-bootstrapped.service

@@ -6,11 +6,11 @@
 [Unit]
 Description=Wait for Tor to Have Bootstrapped
 Documentation=https://tails.boum.org/contribute/design/
+ConditionUser=1000
 
 [Service]
 Type=oneshot
-ExecStart=/bin/sh -c '[ "$(/usr/bin/id -u)" = 1000 ] || exit 0         ; \
-                      while ! [ -e /run/tor-has-bootstrapped/done ] ; do \
+ExecStart=/bin/sh -c 'while ! [ -e /run/tor-has-bootstrapped/done ] ; do \
                          /bin/sleep 1                                  ; \
                       done'
 TimeoutStartSec=0

config/chroot_local-includes/usr/local/lib/add-GNOME-bookmarks

@@ -3,9 +3,6 @@
 set -e
 set -u
 
-# We're a no-op unless running as the default desktop user
-[ "$(/usr/bin/id -u)" = 1000 ] || exit 0
-
 . /usr/local/lib/tails-shell-library/tails-greeter.sh
 
 add_gtk_bookmark_for() {

config/chroot_local-includes/usr/local/lib/create-tor-browser-directories

@@ -3,9 +3,6 @@
 set -e
 set -u
 
-# We're a no-op unless running as the default desktop user
-[ "$(/usr/bin/id -u)" = 1000 ] || exit 0
-
 TOR_BROWSER_AMNESIAC_DIR='/home/amnesia/Tor Browser'
 TOR_BROWSER_PERSISTENT_DIR='/home/amnesia/Persistent/Tor Browser'