Option to disable create/update the user/group running minio & add by default create_home: no

[fititnt]

Refs #43

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This pull request allow disable management from this role for the specified minio_user and minio_group (but by default keep old behavior). The variable used is minio_usergroup_manage: true (We could use other name).

This pull request also implement @SuperQ suggestion from #15 (comment). So by default if this role have to manage user, it will not try create the home directory.

About tests:

• Tested master branch on Ubuntu 18.04 plus these changes (the lastest release had a few changes, so I also tested the master on this PR):
  • The default behavior was keep the like before (except by the create folder)
  • Did not tested full new install (but updated)
• molecule tests to check this nea feature where not added to this initial PR.

Issues to consider when changing in production

this mote was not added to the readme, but will mention here. But this may be intuitive issue, so maybe will not work mention.

When updating the user/group from this role, consider that not only the data directories, but also a folder named .minio.sys at your root data directory may still have the older permissions values and this will make your minio instances restart too quickly.