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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


ip_address:
    description:
      - specifies the address the container will be assigned
  onboot:
    description:
      - specifies whether a VM will be started during system bootup
    type: bool
    default: 'no'
  storage:
    description:
      - target storage
    default: 'local'
  cpuunits:
    description:
      - CPU weight for a VM
    default: 1000
  nameserver:
    description:
      - sets DNS server IP address for a container
  searchdomain:
    description:
      - sets DNS search domain for a container
  timeout:
    description:
      - timeout for operations
    default: 30
  force:
    description:
      - forcing operations
      - can be used only with states C(present), C(stopped), C(restarted)