mysqldump commands on app server get stuck if db server goes away

[balamurali27]

This leads to jobs piling up until the running jobs reach timeout. Happens during backup site tables step of Site Update. Also bench backup cmd.

Maybe --max_statement_time can be easy fix (unsure)

Alternatively, we can have a method for cancelling ongoing jobs and press can cancel jobs on app server when mariadb restarts on db