VMNetXServer: Fix deadlock in GC

state.shutdown() emits the 'destroy' signal, which create_token connects
to VMNetXServer._destroy_token, which in turn requires the same lock that
is held in the gc method.
vmnetx-server: Add option to retrieve server status

Add functionality to be able to query a server for the state of its tokens
and controllers for administrative purposes. Add optional argument which
provides the server with a user identifier for the created token.