step_start_vm_paused: cleanup forces VM shutdown

This allows steps between create_instance and start_vm_paused to assume
that the VM is shut down when cleaning up
Fix error message typo
Add Floppy ConnectVdi type
Add Task class to xapi client
VDI upload, floppy and tools support

This commit add new VDI steps named step_{attach,detach,find,upload}_vdi
  - attach/detach are self-explanatory; can specify CD or Floppy
  - find finds a VDI by name-label and stores the uuid
  - upload uploads a VDI from a local disk image and stores the uuid

In order to demonstrate the new VDI code, this commit trivially adds:
  - support for uploading ISOs again (dependent on unmerged XAPI patch)
  - initial floppy upload/attach support (dependent on currently-broken
    XAPI patch)
  - initial XenServer Tools support
Rename root_disk_size to disk_size

CreateVdi now takes an integer size
Note that disk_size is now in MB; root_disk_size was in bytes
Fixed example
Rename instance_name to vm_name

Fixed example
Rename instance_memory to vm_memory

Note that vm_memory is now in MB; instance_memory was in bytes
SetStaticMemoryRange now takes int64
Fixed example
Don't explicitly remove ISOs in step_remove_devices
Merge pull request #9 from chengsun/master

ISO upload, floppy and tools support, compatibility fixes