Connection aborts is happening in MariaDB 10.2 but not in 10.1 even with log_warnings level set to 2
According to the general consensus that answers shouldn't be posted as comments, following my short answer.
You have set a timeout of 7 minutes and your database instance is aborting the connection after 7 minutes. Works as designed.
General information is logged in the General query log and contains:

Established client connections and statements received from clients

The Error log contains:

Problems encountered starting, running, or stopping mysqld

Reference: 5.4 MySQL Server Logs (MySQL Documentation)
So if your 10.1 installation is not displaying any errors, then you possibly have a larger timeout value set.