Fix virtualization role for DigitalOcean droplets (#41061)

[tomkins]

Fixes #41061

SUMMARY

Fixes ansible_virtualization_role for DigitalOcean droplets - it was incorrectly set to host, this PR changes it to guest.

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

core

ANSIBLE VERSION

ansible 2.6.3
  config file = /Users/tomkins/Admin/blazingfast.net/ansible.cfg
  configured module search path = ['/Users/tomkins/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/tomkins/.virtualenvs/blazingfast/lib/python3.5/site-packages/ansible
  executable location = /Users/tomkins/.virtualenvs/blazingfast/bin/ansible
  python version = 3.5.6 (default, Aug  4 2018, 07:39:57) [GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.2)]

ADDITIONAL INFORMATION

DigitalOcean droplets have the following DMI files available:

root@ubuntu-s-1vcpu-1gb-lon1-01:~# cat /sys/devices/virtual/dmi/id/product_name
Droplet
root@ubuntu-s-1vcpu-1gb-lon1-01:~# cat /sys/devices/virtual/dmi/id/bios_vendor
DigitalOcean
root@ubuntu-s-1vcpu-1gb-lon1-01:~# cat /sys/devices/virtual/dmi/id/sys_vendor
DigitalOcean

Before:

$ ansible -m setup -a "filter=ansible_virtualization_*" ubuntu-s-1vcpu-1gb-lon1-01
ubuntu-s-1vcpu-1gb-lon1-01 | SUCCESS => {
    "ansible_facts": {
        "ansible_virtualization_role": "host",
        "ansible_virtualization_type": "kvm"
    },
    "changed": false
}

After:

$ ansible -m setup -a "filter=ansible_virtualization_*" ubuntu-s-1vcpu-1gb-lon1-01
ubuntu-s-1vcpu-1gb-lon1-01 | SUCCESS => {
    "ansible_facts": {
        "ansible_virtualization_role": "guest",
        "ansible_virtualization_type": "kvm"
    },
    "changed": false
}

I've taken the same approach as #35063 for consistency.

[Akasurde]

cc @BondAnthony

[BondAnthony]

LGTM @Akasurde

[tomkins]

Still impacts Ansible 2.8 - updated PR to match slightly newer style in the file.