Refactor of Remote Instance client

* Moved instance client into Compute namespace
* Moved ping client into Compute namespace
* Added instance client base class
* Simplified functionality provided by instance client
* (unrelated change but necessary to test this code) Added config
  for splitting ephemeral disks

Change-Id: I2ed044436d3c4751afa79e5ba140e160ee67edc1
Merge "Refactor of Remote Instance client"