Managing systems features

[wanix]

Hi,

I add to your roles the followings features:

• managing sysctl vm_overcommit_memory
• kernel transparent hugepages

If not managed, Redis emit a warning

I add the creation of the data directory and the log directory if inexistent too

Thanks for your role

[geerlingguy]

I'd rather split the logfile/log dir part out into a separate PR, as that looks like a change that I may put in (after a little extra testing).

For the other changes, since those can be more OS/server-specific, I'd rather not include those changes in this role—they should really be playbook-level, or a custom role for your particular environment that runs before this role.