Revert "Add -usbdevice tablet to KVM when using vnc"

This reverts commit 5b062a58.
This fixes issue 109. The mouse type can be set with the usb_mouse
hv parameter.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

lib/hypervisor/hv_kvm.py

@@ -547,10 +547,6 @@ class KVMHypervisor(hv_base.BaseHypervisor):
         vnc_arg = 'unix:%s/%s.vnc' % (vnc_bind_address, instance.name)
 
       kvm_cmd.extend(['-vnc', vnc_arg])
-
-      # Also add a tablet USB device to act as a mouse
-      # This solves various mouse alignment issues
-      kvm_cmd.extend(['-usbdevice', 'tablet'])
     else:
       kvm_cmd.extend(['-nographic'])