Blocks a listener (or listeners) launched until vortex finish.
This function should be called after creating a listener (o listeners) calling to vortex_listener_new to block current thread.
This function can be avoided if the program structure can ensure that the programm will not exist after calling vortex_listener_new. This happens when the program is linked to (or implements) and internal event loop.
This function will be unblocked when the vortex listener created ends or a failure have occur while creating the listener. To force an unlocking, a call to vortex_listener_unlock must be done.