Description of problem:
I'm using the rhc system role to register a system using an activation key. When I run the playbook the first time, it succeeds and successfully registers the system.

If I run the playbook again, it fails the second time with an error.

Version-Release number of selected component (if applicable):
RHEL system roles 1.21.1 release from Automation Hub.  

How reproducible:
Every time

Steps to Reproduce:
1.  Run playbook:

- name: Run system roles
  hosts: all
  become: true
  tasks: 
    - name: run rhc system role
      include_role:
        name: redhat.rhel_system_roles.rhc
      vars:
        rhc_state: present
        rhc_auth:
          activation_keys:
            keys: 
              - "<redacted>"
        rhc_organization: "<redacted>"

2. Playbook is successful 
3. Run same playbook again

Actual results:
The second time, the playbook fails:

TASK [redhat.rhel_system_roles.rhc : Call subscription-manager] **********************************************************************************************
fatal: [rhel8-server2.example.com]: FAILED! => {"changed": false, "msg": "parameters are mutually exclusive: activationkey|username"}

Expected results:
Playbook doesn't fail when run again.