It is possible to have a graceful shutdown on running MariaDB/Galera node without removing it from joined cluster?

Currently graceful shutdown removes node from joined cluster. This behavior is unwanted in Docker Compose/Swarm environments. There is a need for additional graceful shutdown signal (maybe USR1) to gracefully shutdown MariadDB daemon and Galera without removing node from cluster.

Simple use case:

• docker-compose up --scale db=3
• docker-compose stop
• All nodes received graceful shutdown signal in the same time from the stop command. In that case, Galera cannot handle this properly and the safe_to_bootstrap variable is not set to 1 in the grastate.dat file on any node. All nodes will fail after next docker-compose up/start invocation.