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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


newid=dict(type='int', default=None),
            node=dict(),
            numa=dict(type='dict'),
            numa_enabled=dict(type='bool'),
            onboot=dict(type='bool', default='yes'),
            ostype=dict(default='l26', choices=['other', 'wxp', 'w2k', 'w2k3', 'w2k8', 'wvista', 'win7', 'win8', 'win10', 'l24', 'l26', 'solaris']),
            parallel=dict(type='dict'),
            pool=dict(type='str'),
            protection=dict(type='bool'),
            reboot=dict(type='bool'),
            revert=dict(type='str', default=None),
            sata=dict(type='dict'),
            scsi=dict(type='dict'),
            scsihw=dict(choices=['lsi', 'lsi53c810', 'virtio-scsi-pci', 'virtio-scsi-single', 'megasas', 'pvscsi']),
            serial=dict(type='dict'),
            shares=dict(type='int'),
            skiplock=dict(type='bool'),
            smbios=dict(type='str'),
            snapname=dict(type='str'),
            sockets=dict(type='int', default=1),
            startdate=dict(type='str'),
            startup=dict(),
            state=dict(default='present', choices=['present', 'absent', 'stopped', 'started', 'restarted', 'current']),
            storage=dict(type='str'),
            tablet=dict(type='bool', default='no'),
            target=dict(type='str'),
            tdf=dict(type='bool'),
            template=dict(type='bool', default='no'),
            timeout=dict(type='int', default=30),
            update=dict(type='bool', default='no'),