Configure system CPUShares for sysinv-agent.service

This reduces sysinv-agent.service cgroup to 256 CPUShare from 1024.
This smoothes out behaviour of poorly behaved audits. CPU usage is
sporadic but not latency critical. There are also extended CPU hog
periods seen during host configuration.

This is part of an overall set of adjustments are required for systemd
cgroups CPUShares, CPUQuota, and AllowedCPUs for for key system services.
This will improve latency of Kubernetes critical components, and
throttles lesser important services.

Partial-Bug: 2084714

TEST PLAN:
AIO-SX, AIO-DX, Standard, Storage, DC:
- PASS: Fresh install
- PASS: verify systemd parameters for sysinv-agent

AIO-SX, AIO-DX:
- PASS: B&R
- PASS: K8S orchestrated upgrades from 1.24 to 1.29

Example:
  systemctl show sysinv-agent.service | grep -e CPUShares

Change-Id: Ice9149b84306356d618efb0a9791cdff91373a5a
Signed-off-by: Jim Gauld <James.Gauld@windriver.com>

sysinv/sysinv-agent/debian/deb_folder/sysinv-agent.service

@@ -11,5 +11,8 @@ ExecStart=/etc/init.d/sysinv-agent start
 ExecStop=/etc/init.d/sysinv-agent stop
 PIDFile=/var/run/sysinv-agent.pid
 
+# cgroup engineering
+CPUShares=256
+
 [Install]
 WantedBy=multi-user.target