Fixup mux initialization
Fixup mux initialization

Make root mux accessible from Service interface.
Creating the service embedded version must not create a version mux
to avoid calling into the select version algorithm when no
version is specified.

smessier/goa,ZjMNZHgG5jMXw/goa,raphael/goa,goadesign/goa,on99/goa,dominicm/goa