Handle warning overcommit_memory

When starting a Redis™* service on Aiven console, you may notice on Logs the following warning overcommit_memory:

# WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.

This warning can be safely ignored as Aiven for Redis™* ensures that the available memory will never drop low enough to hit this particular failure case.