All calls are effectively synchronous, because the tool doesn't exit until it gets a response even in async mode. Yet we maintain two separate code paths: one for `--sync-call`/`cib_sync_call`, and one that uses a main loop.
Ref: https://github.com/ClusterLabs/pacemaker/pull/3403#discussion_r1580492741
This is an easy change but I don't want to grow CLPR#3403 further.