units: install user units as real files, not symlinks to ../system/

This was causing preset-all --global to create symlinks:

$ systemctl preset-all --global --root=/var/tmp/inst1
Created symlink /var/tmp/inst1/etc/systemd/user/shutdown.target → /usr/lib/systemd/user/../system/shutdown.target.
Created symlink /var/tmp/inst1/etc/systemd/user/sockets.target → /usr/lib/systemd/user/../system/sockets.target.
Created symlink /var/tmp/inst1/etc/systemd/user/timers.target → /usr/lib/systemd/user/../system/timers.target.
Created symlink /var/tmp/inst1/etc/systemd/user/paths.target → /usr/lib/systemd/user/../system/paths.target.
Created symlink /var/tmp/inst1/etc/systemd/user/bluetooth.target → /usr/lib/systemd/user/../system/bluetooth.target.
Created symlink /var/tmp/inst1/etc/systemd/user/printer.target → /usr/lib/systemd/user/../system/printer.target.
Created symlink /var/tmp/inst1/etc/systemd/user/sound.target → /usr/lib/systemd/user/../system/sound.target.
Created symlink /var/tmp/inst1/etc/systemd/user/smartcard.target → /usr/lib/systemd/user/../system/smartcard.target.
Created symlink /var/tmp/inst1/etc/systemd/user/busnames.target → /usr/lib/systemd/user/../system/busnames.target.

It is better to create units in a state that completely matches the presets, i.e.
preset-all should do nothing when invoked immediately after installation.

I'm sure it was confusing to users too, suggesting that system and user units
may somehow alias each other.

1 files changed, 1 insertions, 0 deletions

diff --git a/units/user/sound.target b/units/user/sound.target
new file mode 120000
index 0000000000..17c8e9d6e1
--- /dev/null
+++ b/units/user/sound.target
@@ -0,0 +1 @@
+../sound.target
\ No newline at end of file