conf: free the ports array of a USB hub

The array needs to be freed too, not just its members.

https://bugzilla.redhat.com/show_bug.cgi?id=1366097

src/conf/domain_addr.c

@@ -1360,6 +1360,7 @@ virDomainUSBAddressHubFree(virDomainUSBAddressHubPtr hub)
 
     for (i = 0; i < hub->nports; i++)
         virDomainUSBAddressHubFree(hub->ports[i]);
+    VIR_FREE(hub->ports);
     virBitmapFree(hub->portmap);
     VIR_FREE(hub);
 }