refactoring: rename variable in getVlanID function

In the function getVlanID we're using id as a variable
name, proposed refactoring changes this variable name,
so we don't redefine the built-in function 'id'.

Change-Id: I16f28ea07c3ba0a704a094f0fa08d4e03b07a9dc
Signed-off-by: Giuseppe Vallarelli <gvallare@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/17830
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>