Close minor startup race between main and scheduler threads

Don't schedule class PeerManagerImpl's background tasks from its
constructor, but instead do that from a separate method,
StartScheduledTasks(), that can be called later at the end of startup,
after other things, such as the active chain, are initialzed.

src/init.cpp

@@ -1180,7 +1180,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 
     assert(!node.peerman);
     node.peerman = PeerManager::make(chainparams, *node.connman, *node.addrman, node.banman.get(),
-                                     *node.scheduler, chainman, *node.mempool, ignores_incoming_txs);
+                                     chainman, *node.mempool, ignores_incoming_txs);
     RegisterValidationInterface(node.peerman.get());
 
     // sanitize comments per BIP-0014, format user agent and check total size
@@ -1789,6 +1789,8 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         banman->DumpBanlist();
     }, DUMP_BANS_INTERVAL);
 
+    if (node.peerman) node.peerman->StartScheduledTasks(*node.scheduler);
+
 #if HAVE_SYSTEM
     StartupNotify(args);
 #endif