use grub/shim from host system

Also the boot method is now configured globaly as this is
the only way to make sure that unkonwn nodes get the right
stuff

Signed-off-by: Christian Goll <cgoll@suse.com>

internal/pkg/warewulfd/warewulfd.go

@@ -65,7 +65,6 @@ func RunServer() error {
 		wwlog.Error("Could not prepopulate node status DB: %s", err)
 	}
 
-	err = CopyShimGrub()
 	if err != nil {
 		wwlog.Warn("couldn't copy default shim: %s", err)
 	}