message: Use empty map as cgroups attribute default
diff: @@ -79,6 +79,7 @@ pub struct CpuResources {
  /// This is currently a no-operation.
  pub realtime_period: Option<u64>,
  /// Customized key-value attributes
  + #[serde(default, skip_serializing_if = "HashMap::is_empty")]
  pub attrs: HashMap<String, String>,
  }
  @@ -103,5 +104,6 @@ pub struct MemoryResources {
  /// traditional `mlock(2)` system call for that purpose.
  pub swappiness: Option<u64>,
  /// Customized key-value attributes
  + #[serde(default, skip_serializing_if = "HashMap::is_empty")]
  pub attrs: HashMap<String, String>,
  }
  