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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


shares:
    description:
      - Rets amount of memory shares for auto-ballooning. (0 - 50000).
      - The larger the number is, the more memory this VM gets.
      - The number is relative to weights of all other running VMs.
      - Using 0 disables auto-ballooning, this means no limit.
  skiplock:
    description:
      - Ignore locks
      - Only root is allowed to use this option.
  smbios:
    description:
      - Specifies SMBIOS type 1 fields.
  snapname:
    description:
      - The name of the snapshot. Used only with clone.
  sockets:
    description:
      - Sets the number of CPU sockets. (1 - N).
    default: 1
  startdate:
    description:
      - Sets the initial date of the real time clock.
      - Valid format for date are C('now') or C('2016-09-25T16:01:21') or C('2016-09-25').
  startup:
    description:
      - Startup and shutdown behavior. C([[order=]\d+] [,up=\d+] [,down=\d+]).
      - Order is a non-negative number defining the general startup order.
      - Shutdown in done with reverse ordering.
  state: