Parallel execution for tasks

[erdincka]

Some tasks can run in parallel, ie, "add workers" and "configure DF node", "create k8scluster" and "create DF".
Currently running Samba in docker container within ad_server is started as async task, and is never checked for completion/errors. Would be nice to have a method to submit tasks in the background, and check/wait just before the job that depends it (create tenant should check create cluster, install mapr should check AD integration etc).
Ansible has async method, and I guess it is the best option to implement this (need to ensure we submit and check these jobs on the same hosts etc).