<!--- Verify first that your issue is not already reported on GitHub -->
<!--- Also test if the latest release and devel branch are affected too -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### 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


elif not node_check(proxmox, node):
                module.fail_json(msg="node '%s' not exists in cluster" % node)
            elif not content_check(proxmox, node, module.params['ostemplate'], template_store):
                module.fail_json(msg="ostemplate '%s' not exists on node %s and storage %s"
                                 % (module.params['ostemplate'], node, template_store))
            create_instance(module, proxmox, vmid, node, disk, storage, cpus, memory, swap, timeout,
                            cores=module.params['cores'],
                            pool=module.params['pool'],
                            password=module.params['password'],
                            hostname=module.params['hostname'],
                            ostemplate=module.params['ostemplate'],
                            netif=module.params['netif'],
                            mounts=module.params['mounts'],
                            ip_address=module.params['ip_address'],
                            onboot=int(module.params['onboot']),
                            cpuunits=module.params['cpuunits'],
                            nameserver=module.params['nameserver'],
                            searchdomain=module.params['searchdomain'],
                            force=int(module.params['force']),
                            pubkey=module.params['pubkey'],
                            unprivileged=int(module.params['unprivileged']))
            module.exit_json(changed=True, msg="deployed VM %s from template %s" % (vmid, module.params['ostemplate']))
        except Exception as e:
            module.fail_json(msg="creation of %s VM %s failed with exception: %s" % (VZ_TYPE, vmid, e))
    elif state == 'started':
        try:
            vm = get_instance(proxmox, vmid)
            if not vm:
                module.fail_json(msg='VM with vmid = %s not exists in cluster' % vmid)
            if getattr(proxmox.nodes(vm[0]['node']), VZ_TYPE)(vmid).status.current.get()['status'] == 'running':