Build: split out egg-info Makefile target from version-update target
    
    This is temporary workaround necessary until we throw away the hand-made
    Makefile. ipaplatform is going to be managed by configure, but configure
    right now depends on version-update target in Makefile.
    
    https://fedorahosted.org/freeipa/ticket/6418
    
    Reviewed-By: Lukas Slebodnik <lslebodn@redhat.com>
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>