bump users role to v1.5.3: many improvements
bump users role to v1.5.3: many improvements

 - https://github.com/CSC-IT-Center-for-Science/ansible-role-users/releases/tag/v1.5.3
  - set comment= and remove= and only remove passwords on present users
 - https://github.com/CSC-IT-Center-for-Science/ansible-role-users/releases/tag/v1.5.2
  - use package module, install libselinux and use group and groups
 - https://github.com/CSC-IT-Center-for-Science/ansible-role-users/releases/tag/v1.5.1
  - actually remove users and keys
 - https://github.com/CSC-IT-Center-for-Science/ansible-role-users/releases/tag/v1.5.0
  - use block and default(omit) to reduce tasks

mantti/fgci-tut,mantti/fgci-tut,mantti/fgci-tut