Merge bitcoin/bitcoin#25887: init: avoid unsetting service bits from nLocalServices

1b5bec7 init: avoid unsetting service bits from `nLocalServices` (Sebastian Falbesoner)

Pull request description:

  This PR is a late follow-up to the [review club session about the PR "Default to NODE_WITNESS in nLocalServices" ](https://bitcoincore.reviews/21090#l-90) (#21090):

  ```
  17:32 <lightlike> hmm, if we are in pruned mode, we first set NODE_NETWORK and then unset it later in init.cpp. that seems a bit strange.
  ...
  17:33 <jnewbery> lightlike: ah yes, you're right. That does seem a bit messy.
  ```

  Rather than setting the service bit `NODE_NETWORK` first and then unset it (if in `fPruneMode`), start with the bare minimum flags that we always serve and only add `NODE_NETWORK` if we are running as a non-pruned node. This seems to be a more logical approach than currently on master.

ACKs for top commit:
  naumenkogs:
    ACK 1b5bec7
  stickies-v:
    ACK 1b5bec7
  LarryRuane:
    ACK 1b5bec7

Tree-SHA512: 2e82d66c4298ffacff41d9e0458b74b83bc156a1fa49e3f3471e942878e5dd2b253b5597ee5ec1d9c8726b432751d05e40f0c580f3976a9e00a7d1f417921ab0

Author: MacroFake

src/init.cpp

@@ -742,7 +742,7 @@ namespace { // Variables internal to initialization process only
 int nMaxConnections;
 int nUserMaxConnections;
 int nFD;
-ServiceFlags nLocalServices = ServiceFlags(NODE_NETWORK | NODE_NETWORK_LIMITED | NODE_WITNESS);
+ServiceFlags nLocalServices = ServiceFlags(NODE_NETWORK_LIMITED | NODE_WITNESS);
 int64_t peer_connect_timeout;
 std::set<BlockFilterType> g_enabled_filter_types;
 
@@ -1519,18 +1519,19 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 
     // ********************************************************* Step 10: data directory maintenance
 
-    // if pruning, unset the service bit and perform the initial blockstore prune
+    // if pruning, perform the initial blockstore prune
     // after any wallet rescanning has taken place.
     if (fPruneMode) {
-        LogPrintf("Unsetting NODE_NETWORK on prune mode\n");
-        nLocalServices = ServiceFlags(nLocalServices & ~NODE_NETWORK);
         if (!fReindex) {
             LOCK(cs_main);
             for (CChainState* chainstate : chainman.GetAll()) {
                 uiInterface.InitMessage(_("Pruning blockstore…").translated);
                 chainstate->PruneAndFlush();
             }
         }
+    } else {
+        LogPrintf("Setting NODE_NETWORK on non-prune mode\n");
+        nLocalServices = ServiceFlags(nLocalServices | NODE_NETWORK);
     }
 
     // ********************************************************* Step 11: import blocks