vmwareapi: remove unused update_host_status method

The VMWare driver declares a method 'update_host_status'
which has no callers anywhere in the codebase.

This is left over code that was missed in the cleanup from

  commit 2cb47fbabf09ced76178e8453d508c66f86a7a3a
  Author: Arata Notsu <notsu@virtualtech.jp>
  Date:   Thu Oct 18 22:40:01 2012 +0900

    Remove ComputeDriver.update_host_status()

Partial-bug: #1333219
Change-Id: Ie0de9b6d427246cb3c3adb818d483b61dfb08d82
Merge "vmwareapi: remove unused update_host_status method"