Old systemd in el7 doesn't allow slash "/" in RuntimeDirectory. Please replace it with "ExecStartPre=mkdir -p /run/lock/netatalk" in el7.

See epel7 build log:

#error Do not use this file, it is the result of a failed Cython compilation.
WARNING: Failed to compile extension modules.
msgpack uses fallback pure python implementation.

This results following error when running borg:

Using a pure-python msgpack! This will result in lower performance.

Borg works, but emits above warning.