rust-agent: Remove or rename unused parameters

Parameters that are never used were removed.
Parameters that are unused, but necessary because of some common
interface were renamed with a _ prefix.
In one case, consume the parameter by adding an info! call, and fix a
minor typo in a message in the same function.

This addresses the following warning:

    warning: unused variable: `child`
        --> rustjail/src/container.rs:1128:5
         |
    1128 |     child: &mut Child,
         |     ^^^^^ help: if this is intentional, prefix it with an underscore: `_child`

    warning: unused variable: `logger`
        --> rustjail/src/container.rs:1049:22
         |
    1049 | fn update_namespaces(logger: &Logger, spec: &mut Spec, init_pid: RawFd) -> Result<()> {
         |                      ^^^^^^ help: if this is intentional, prefix it with an underscore: `_logger`

Fixes: #750

Signed-off-by: Christophe de Dinechin <dinechin@redhat.com>

src/agent/rustjail/src/cgroups/fs/mod.rs

@@ -230,7 +230,7 @@ impl CgroupManager for Manager {
 }
 
 fn set_network_resources(
-    cg: &cgroups::Cgroup,
+    _cg: &cgroups::Cgroup,
     network: &LinuxNetwork,
     res: &mut cgroups::Resources,
 ) -> Result<()> {
@@ -259,7 +259,7 @@ fn set_network_resources(
 }
 
 fn set_devices_resources(
-    cg: &cgroups::Cgroup,
+    _cg: &cgroups::Cgroup,
     device_resources: &Vec<LinuxDeviceCgroup>,
     res: &mut cgroups::Resources,
 ) -> Result<()> {
@@ -288,7 +288,7 @@ fn set_devices_resources(
 }
 
 fn set_hugepages_resources(
-    cg: &cgroups::Cgroup,
+    _cg: &cgroups::Cgroup,
     hugepage_limits: &Vec<LinuxHugepageLimit>,
     res: &mut cgroups::Resources,
 ) -> Result<()> {

src/agent/rustjail/src/container.rs

@@ -888,7 +888,6 @@ impl BaseContainer for LinuxContainer {
             &p,
             self.cgroup_manager.as_ref().unwrap(),
             &st,
-            &mut child,
             pwfd,
             prfd,
         ) {
@@ -1039,8 +1038,9 @@ fn do_exec(args: &[String]) -> ! {
 }
 
 fn update_namespaces(logger: &Logger, spec: &mut Spec, init_pid: RawFd) -> Result<()> {
+    info!(logger, "updating namespaces");
     let linux = match spec.linux.as_mut() {
-        None => return Err(anyhow!("Spec didn't container linux field")),
+        None => return Err(anyhow!("Spec didn't contain linux field")),
         Some(l) => l,
     };
 
@@ -1117,7 +1117,6 @@ fn join_namespaces(
     p: &Process,
     cm: &FsManager,
     st: &OCIState,
-    _child: &mut Child,
     pwfd: RawFd,
     prfd: RawFd,
 ) -> Result<()> {