Adding function to modify VM settings

[pradipd]

This is needed by GPU because we modify the VM settings after we create the VM.

[pradipd]

Note: the unit test was not compiling. I cleaned it up so it compiles, but it is still failing.
the GPU test fails because it needs to run on gpu machine. that's fine.
but, a few others are failing. I spent a little time debugging but, had to give up.