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/test/util/setup_common.cpp

@@ -197,7 +197,7 @@ TestingSetup::TestingSetup(const std::string& chainName, const std::vector<const
     m_node.banman = std::make_unique<BanMan>(m_args.GetDataDirBase() / "banlist", nullptr, DEFAULT_MISBEHAVING_BANTIME);
     m_node.connman = std::make_unique<CConnman>(0x1337, 0x1337, *m_node.addrman); // Deterministic randomness for tests.
     m_node.peerman = PeerManager::make(chainparams, *m_node.connman, *m_node.addrman,
-                                       m_node.banman.get(), *m_node.scheduler, *m_node.chainman,
+                                       m_node.banman.get(), *m_node.chainman,
                                        *m_node.mempool, false);
     {
         CConnman::Options options;