scripts: policy-node: wait for unactivated links instead of removing

If a link is not activated, don't remove it. Instead, schedule a rescan
when a link activates, so that we'll handle it once it does.

This is a workaround for some problems, see
https://github.com/Audio4Linux/JDSP4Linux/issues/74
However, the underlying cause is not understood.

src/scripts/policy-node.lua

@@ -123,6 +123,7 @@ function createLink (si, si_target, passthrough, exclusive)
       end
       Log.info (l, "activated si-standard-link")
     end
+    scheduleRescan()
   end)
 end
 
@@ -696,9 +697,11 @@ function handleLinkable (si)
       if link ~= nil then
         -- remove old link
         if ((link:get_active_features() & Feature.SessionItem.ACTIVE) == 0) then
-          -- remove also not yet activated links: they might never become active,
-          -- and we should not loop waiting for them
-          Log.warning (link, "Link was not activated before removing")
+          -- Link not yet activated. We don't want to remove it now, as that
+          -- may cause problems. Instead, give up for now. A rescan is scheduled
+          -- once the link activates.
+          Log.info (link, "Link to be moved was not activated, will wait for it.")
+          return
         end
         si_flags[si_id].peer_id = nil
         link:remove ()