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##### SUMMARY
An hour ago I upgraded my Proxmox to the new stable version 6. Since then my playbooks fail with this error:
`fatal: [proxmox]: FAILED! => {"changed": false, "msg": "authorization on proxmox cluster failed with exception: could not convert string to float: '6.0-4'"}`

It seems like the proxmox changed the API.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
proxmox (https://github.com/mrdrogdrog/ansible/blob/6430205d396b7c1733de22a898c51823f67d5bf4/lib/ansible/modules/cloud/misc/proxmox.py#L484)

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```
ansible 2.8.2
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/home/tilman/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python3.7/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 3.7.3 (default, Jun 24 2019, 04:54:02) [GCC 9.1.0]
```


##### OS / ENVIRONMENT
Proxmox 6 


##### STEPS TO REPRODUCE
- Use the latest ansible version
- Use the latest stable version of proxmox (6)
- Use the proxmox module to do anything. E.g. create a container
- Get the error


##### EXPECTED RESULTS
Normal runthrough

##### ACTUAL RESULTS
Crash with an error


cpuunits=dict(type='int', default=1000),
            nameserver=dict(),
            searchdomain=dict(),
            timeout=dict(type='int', default=30),
            force=dict(type='bool', default='no'),
            state=dict(default='present', choices=['present', 'absent', 'stopped', 'started', 'restarted']),
            pubkey=dict(type='str', default=None),
            unprivileged=dict(type='bool', default='no')
        )
    )
    if not HAS_PROXMOXER:
        module.fail_json(msg='proxmoxer required for this module')
    state = module.params['state']
    api_user = module.params['api_user']
    api_host = module.params['api_host']
    api_password = module.params['api_password']
    vmid = module.params['vmid']
    validate_certs = module.params['validate_certs']
    node = module.params['node']
    disk = module.params['disk']
    cpus = module.params['cpus']
    memory = module.params['memory']
    swap = module.params['swap']
    storage = module.params['storage']
    hostname = module.params['hostname']
    if module.params['ostemplate'] is not None:
        template_store = module.params['ostemplate'].split(":")[0]
    timeout = module.params['timeout']
    
    if not api_password: