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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


kvm=module.params['kvm'],
                      localtime=module.params['localtime'],
                      lock=module.params['lock'],
                      machine=module.params['machine'],
                      migrate_downtime=module.params['migrate_downtime'],
                      migrate_speed=module.params['migrate_speed'],
                      net=module.params['net'],
                      numa=module.params['numa'],
                      numa_enabled=module.params['numa_enabled'],
                      onboot=module.params['onboot'],
                      ostype=module.params['ostype'],
                      parallel=module.params['parallel'],
                      pool=module.params['pool'],
                      protection=module.params['protection'],
                      reboot=module.params['reboot'],
                      sata=module.params['sata'],
                      scsi=module.params['scsi'],
                      scsihw=module.params['scsihw'],
                      serial=module.params['serial'],
                      shares=module.params['shares'],
                      skiplock=module.params['skiplock'],
                      smbios1=module.params['smbios'],
                      snapname=module.params['snapname'],
                      startdate=module.params['startdate'],
                      startup=module.params['startup'],
                      tablet=module.params['tablet'],
                      target=module.params['target'],
                      tdf=module.params['tdf'],
                      template=module.params['template'],
                      vcpus=module.params['vcpus'],