Before the OCF Resource Agent API 1.1 standard introduced the `reload-agent` action and the `reloadable` parameter meta-data attribute, Pacemaker supported using the `reload` action with the `unique` attribute. Only Pacemaker agents are known to have used this extension.
Pacemaker 2.1.0 introduced support for `reload-agent` and deprecated support for `reload`. Once we no longer support rolling upgrades from <2.1.0 (see subtask), we can drop the deprecated support. See code for `ra_supports_legacy_reload` and `PCMK_ACTION_RELOAD`.