Organize tasks Phase 1

[dtwersky]

The tasks folder has become a bit cluttered. This is phase 1 to organizing the tasks based on what component that task is working on. This only splits out tasks related to the OS settings. The next phases will split the splunk related tasks and variable setting tasks.

Splitting out these tasks will allow the role to be more idempotent, so we don't need to run a monolithic task like check_splunk.yml which needs just to do some checks, as well as move things out of main.yml.

For now, I just moved all tasks related to the OS configuration to its own folder.
I moved the user creation and configuration outside of the install_splunk.yml and into its own task under the os_common directory.

This also splits out certain tasks into their own smaller tasks, which will allow to limit to a specific task, like fixing configuration issues. For example, if the user was not set up correctly, you cannot use the playbook to fix that part is in the install_splunk.yml task, which will not run if splunk is already installed. With this, you can add -e deployment_task=os_common/configure_user.yml, and only that part will run.

This PR includes a fix for the DMC configuration as well.