bluez5_utils: Make systemd link correctly

The link in /etc/systemd/system/, named dbus-org.bluez.service, pointing to
../../../../usr/lib/systemd/system/bluetooth.service has one too many ".." in
it.  Likely the target was copied from the other link in
/etc/systemd/system/bluetooth.target.wants/, which is one level deeper.

Adjust link to be correct.

Signed-off-by: Trent Piepho <tpiepho@impinj.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>