Micah, According to your logs, you had mysql-server 5.5.54-0+deb8u1 and then upgraded to mysql-server 5.6.30-1. So your bug is about MySQL, not about MariaDB. The libmariadbclient18 library you had installed does not affect mysqld before or after in any way.
Indeed Bug#800588 is filed agains mysql-server, which is no longer in Debian Stretch. For the time being I am trying to focus on Stretch issues as it is close to freeze and release.
