Bug 86076

Attempt to enable a unit which has been symlinked into the search path by `systemctl link` produces the following error message:
"Failed to execute operation: No such file or directory."

Also the `systemctl link` itself generates a warning-level message in the log:
"Unknown serialization item 'subscribed=:1.1'"

$ cat /test.service 
[Unit]
Description=Test service

[Service]
Type=oneshot
ExecStart=/bin/true

[Install]
WantedBy=multi-user.target

$ sudo systemctl link /test.service 
Created symlink from /etc/systemd/system/test.service to /test.service.

$ sudo systemctl enable test.service
Failed to execute operation: No such file or directory

$ journalctl -n1 _PID=1 -p warning
-- Logs begin at Ср 2014-10-15 14:29:58 MSK, end at Вс 2014-11-09 23:00:11 MSK. --
ноя 09 23:00:07 intelfx-laptop systemd[1]: Unknown serialization item 'subscribed=:1.1'