agent: correct CPUShares and CPUWeight value

If cgroup driver is systemd, CPUShares, for cgroup v1, should be at
least 2 [1] and CPUWeight for cgroup v2, should be at least 1 [2].

Fixes: #8340
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>

[1] https://github.com/systemd/systemd/blob/d19434fbf81db04d03c8cffa87821f754a86635b/src/basic/cgroup-util.h#L122
[2] https://github.com/systemd/systemd/blob/d19434fbf81db04d03c8cffa87821f754a86635b/src/basic/cgroup-util.h#L91

src/agent/rustjail/src/cgroups/systemd/subsystem/cpu.rs

@@ -50,7 +50,10 @@ impl Cpu {
         systemd_version: &str,
     ) -> Result<()> {
         if let Some(shares) = cpu_resources.shares {
-            properties.push(("CPUShares", Value::U64(shares)));
+            // Minimum value of CPUShares should be 2, see https://github.com/systemd/systemd/blob/d19434fbf81db04d03c8cffa87821f754a86635b/src/basic/cgroup-util.h#L122
+            if shares >= 2 {
+                properties.push(("CPUShares", Value::U64(shares)));
+            }
         }
 
         if let Some(period) = cpu_resources.period {
@@ -81,7 +84,9 @@ impl Cpu {
     ) -> Result<()> {
         if let Some(shares) = cpu_resources.shares {
             let weight = shares_to_weight(shares);
-            properties.push(("CPUWeight", Value::U64(weight)));
+            if weight != 0 {
+                properties.push(("CPUWeight", Value::U64(weight)));
+            }
         }
 
         if let Some(period) = cpu_resources.period {