discovery: use a no-op hash accumluator for local networks

If LND is running on a local network, then use deterministic sampling so
that we can have deterministic peer bootstrapping.

docs/release-notes/release-notes-0.20.0.md

@@ -144,7 +144,9 @@ reader of a payment request.
   disabling has now been 
   [removed](https://github.com/lightningnetwork/lnd/pull/9967) meaning that any 
   test network scripts that rely on bootstrapping being disabled will need to 
-  explicitly define the `--nobootstrap` flag.
+  explicitly define the `--nobootstrap` flag. Bootstrapping will now also be
+  [deterministic](https://github.com/lightningnetwork/lnd/pull/10003) on local 
+  test networks so that bootstrapping behaviour can be tested for.
 
 ## Database