spec: Remove admin package specification
    
    Its only file must be included in the daemon package anyway, since the
    daemon is linked with the admin library and so then it's just an empty
    package until we have virt-admin binary which we can decide later on
    whether to just move it to clients or create a new package for it.
    
    Signed-off-by: Martin Kletzander <mkletzan@redhat.com>