Run the Parsec service as parsec user in /var/lib/parsec/ working directory.

Signed-off-by: Anton Antonov <Anton.Antonov@arm.com>
Upstream-Status: Inappropriate [deployment configuration]

--- a/systemd-daemon/parsec.service	2021-03-28 18:34:18.703196235 +0100
+++ b/systemd-daemon/parsec.service	2021-03-28 18:35:14.279830299 +0100
@@ -3,7 +3,9 @@
 Documentation=https://parallaxsecond.github.io/parsec-book/parsec_service/install_parsec_linux.html
 
 [Service]
-WorkingDirectory=/home/parsec/
+User=parsec
+Group=parsec
+WorkingDirectory=/var/lib/parsec/
 ExecStart=/usr/libexec/parsec/parsec --config /etc/parsec/config.toml
 
 [Install]