Selenium not working correctly on systemd distros

[geerlingguy]

Currently, Selenium installation fails under Ansible 2.2.x when using any distro that uses systemd:

TASK [arknoll.selenium : Include OS-Specific variables] ************************
ok: [drupalvm]

TASK [arknoll.selenium : Install dependencies] *********************************
ok: [drupalvm]

TASK [arknoll.selenium : create directory] *************************************
changed: [drupalvm]

TASK [arknoll.selenium : Download Selenium] ************************************
changed: [drupalvm]

TASK [arknoll.selenium : Install FireFox (if configured)] **********************
skipping: [drupalvm]

TASK [arknoll.selenium : Install Chrome (if configured, Debian)] ***************
changed: [drupalvm]

TASK [arknoll.selenium : Install Chrome (if configured, RedHat)] ***************
skipping: [drupalvm]

TASK [arknoll.selenium : Get the latest release for chromedriver] **************
ok: [drupalvm]

TASK [arknoll.selenium : Install chromedriver] *********************************
changed: [drupalvm]

TASK [arknoll.selenium : Install xvfb] *****************************************
changed: [drupalvm]

TASK [arknoll.selenium : Install init script] **********************************
changed: [drupalvm]

TASK [arknoll.selenium : Ensure selenium is running] ***************************
fatal: [drupalvm]: FAILED! => {"changed": false, "failed": true, "msg": "Could not find the requested service \"'selenium'\": "}

The upstream role has released a 2.1.0 update that supplies a unit file and should work correctly on Ubuntu 16.04, Debian 8, and CentOS 7 (it also makes the Chrome installation a little more robust): https://github.com/arknoll/ansible-role-selenium/releases/tag/2.1.0

We should update Drupal VM to use the latest version.