Optimization for MongoDB and redis - disable hugepages

[unsystemizer]

We could suggest 2 modifications on the host (to disable transparent hugepages in host OS boot settings)

The same should be done for redis container. It also needs some other tweaks. Here's what I saw with fednode on April 30, 2017:

redis_1                 | 1:M 30 Apr 08:37:03.294 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
redis_1                 | 1:M 30 Apr 08:37:03.294 # Server started, Redis version 3.2.8
redis_1                 | 1:M 30 Apr 08:37:03.294 # 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.
redis_1                 | 1:M 30 Apr 08:37:03.294 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.

[unsystemizer]

Just realized that it can be done in newer versions of Docker:
moby/moby#19265

But considering that people who install FedNode may not necessarily be aware of these changes (if they were to be implemented in our Compose templates), I think it's better to simply document that in Federated Node documentation that these tweaks can be applied manually for more demanding Federated Node environments.