Fix user creation for multiple cluster deployments

[stvslim-gm]

Description

When provisioning multiple clusters from a single playbook, the user creation step currently runs only for one cluster.
These changes ensure that user creation is executed for each cluster.

Example playbook:

- name: install galera cluster
  hosts: galera_cluster
  become: true
  roles:
    - mariadb_galera

Example inventory:

cluster-1-host-1 ansible_ssh_host=192.168.1.1
cluster-1-host-2 ansible_ssh_host=192.168.1.2
cluster-1-host-3 ansible_ssh_host=192.168.1.3

cluster-2-host-1 ansible_ssh_host=192.168.2.1
cluster-2-host-2 ansible_ssh_host=192.168.2.2
cluster-2-host-3 ansible_ssh_host=192.168.2.3


[galera_cluster_1]
cluster-1-host-1
cluster-1-host-2
cluster-1-host-3

[galera_cluster_1:vars]
galera_cluster_nodes_group=galera_cluster_1

[galera_cluster_2]
cluster-2-host-1
cluster-2-host-2
cluster-2-host-3

[galera_cluster_2:vars]
galera_cluster_nodes_group=galera_cluster_2

[galera_cluster:child]
galera_cluster_1
galera_cluster_2

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (non-breaking change that does not add functionality or fix an issue)

Checklist:

• I have read the CONTRIBUTING document.
• I have run the pre-merge tests locally and they pass.