Issue #3293949: Set the MySQL transaction isolation level (READ COMMITTED)

.tugboat/config.yml

@@ -151,6 +151,9 @@ services:
 
         # The settings must be written after enabling the memcache module.
         tee -a "${SETTINGS_FILE}" > /dev/null << EOF
+        \$databases['default']['default']['init_commands'] = [
+          'isolation_level' => 'SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED',
+        ];
         \$settings['memcache']['servers'] = ['memcached:11211' => 'default'];
         \$settings['memcache']['bins'] = ['default' => 'default'];
         \$settings['memcache']['key_prefix'] = 'cloud_orchestrator';