Comment 4 for bug 2060644

Thanks @ggouzi

So the charm "ought" to be using /usr/sbin/nologin as the shell, according to this code in (https://opendev.org/openstack/charm-mysql-router/src/commit/46c5d68b7256cd4f9416cc5578a77205da0be493/src/lib/charm/openstack/mysql_router.py#L299):

        if not ch_core.host.user_exists(self.mysqlrouter_user):
            ch_core.host.adduser(
                self.mysqlrouter_user, shell="/usr/sbin/nologin",
                system_user=True, primary_group=self.mysqlrouter_group,
                home_dir=self.mysqlrouter_home_dir)

So perhaps something else is adding the /bin/sh for mysql-router? Is the mysql-client installed?