Adding support for Serial Ports

[seanpmassey]

/kind feature

Describe the solution you'd like
The Nutanix AHV plugin lacks support for configuring Serial Ports. This feature would allow a user to configure a serial port when provisioning a new VM.

Anything else you would like to add:
Debian and Ubuntu distribute pre-configured Cloud images in QCOW2 and RAW format that can be imported into a Nutanix environment. These images, however, are configured to enable printing information to the serial console, and the images will experience a kernel panic or hang during their first boot if a serial port is not present.

The Nutanix documentation covers creating an Ubuntu Cloud Image-based VM here: https://portal.nutanix.com/page/documents/kbs/details?targetId=kA00e000000CshJCAS. This article includes an API sample for creating a new VM with a Serial Port.