xm: xen-api, pass-through: create: Use vslot for hotplug_slot

Using func for hotplug_slot is not correct, although func is often
zero, previously zero meant please pick a vslot and asking xend to
pick a vslot was the only method available.

This resolves the following error when using Xen API:
$ xm create hvm.conf
...
Internal error: Timed out waiting for device model action.

Signed-off-by: Simon Horman <horms@verge.net.au>

tools/python/xen/xm/xenapi_create.py

@@ -539,7 +539,7 @@ class xenapi_create:
             "PPCI":
                 target_ref,
             "hotplug_slot":
-                int(pci.attributes["func"].value, 16),
+                int(pci.attributes["vslot"].value, 16),
             "options":
                 get_child_nodes_as_dict(pci,
                   "pci_opt", "key", "value")