New 'Normal shutdown' log format can be confusing

After MDEV-8491, normal shutdown is logged like this:

[Note] /bld/10.2/bin/mysqld (root[root] @ localhost [::1]): Normal shutdown

It's questionable whether it's pretty or not, but it's understandable. However, when a server is SIGTERM-ed rather than shut down, it gets uglier:

[Note] /bld/10.2/bin/mysqld (unknown): Normal shutdown

Unknown what, mysqld?
I think the format initially requested by Ivan is better, it's really not the best place to save on symbols. It can also be a combination of the requested and implemented formats:

[Note] /bld/10.2/bin/mysqld (initiated by: root[root] @ localhost [::1]): Normal shutdown

[Note] /bld/10.2/bin/mysqld (initiated by: unknown): Normal shutdown