state: fix race condition when reading cgroup

by the time crun attempts to read from the cgroup, systemd might have
already cleaned it up.  When using systemd, on ENOENT state reports
the container as "stopped" instead of an error.

Closes: containers/podman#7148

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

src/libcrun/container.c

@@ -2194,7 +2194,17 @@ libcrun_get_container_state_string (const char *id, libcrun_container_status_t *
 
       ret = libcrun_cgroup_is_container_paused (status->cgroup_path, cgroup_mode, &paused, err);
       if (UNLIKELY (ret < 0))
-        return ret;
+        {
+          /* The cgroup might have been cleaned up by systemd by the time we try to read it, so ignore ENOENT.  */
+          if (status->systemd_cgroup && crun_error_get_errno (err) == ENOENT)
+            {
+              crun_error_release (err);
+              *container_status = "stopped";
+              return 0;
+            }
+
+          return ret;
+        }
     }
 
   if (! *running)