Move scheduler/threadGroup into common-init instead of per-app

This resolves #12229 which pointed out a shutdown deadlock due to
scheduler/checkqueue having been shut down while network message
processing is still running.

src/bitcoind.cpp

@@ -14,7 +14,6 @@
 #include <rpc/server.h>
 #include <init.h>
 #include <noui.h>
-#include <scheduler.h>
 #include <util.h>
 #include <httpserver.h>
 #include <httprpc.h>
@@ -40,7 +39,7 @@
  * Use the buttons <code>Namespaces</code>, <code>Classes</code> or <code>Files</code> at the top of the page to start navigating the code.
  */
 
-void WaitForShutdown(boost::thread_group* threadGroup)
+void WaitForShutdown()
 {
     bool fShutdown = ShutdownRequested();
     // Tell the main threads to shutdown.
@@ -49,11 +48,7 @@ void WaitForShutdown(boost::thread_group* threadGroup)
         MilliSleep(200);
         fShutdown = ShutdownRequested();
     }
-    if (threadGroup)
-    {
-        Interrupt(*threadGroup);
-        threadGroup->join_all();
-    }
+    Interrupt();
 }
 
 //////////////////////////////////////////////////////////////////////////////
@@ -62,9 +57,6 @@ void WaitForShutdown(boost::thread_group* threadGroup)
 //
 bool AppInit(int argc, char* argv[])
 {
-    boost::thread_group threadGroup;
-    CScheduler scheduler;
-
     bool fRet = false;
 
     //
@@ -165,7 +157,7 @@ bool AppInit(int argc, char* argv[])
             // If locking the data directory failed, exit immediately
             return false;
         }
-        fRet = AppInitMain(threadGroup, scheduler);
+        fRet = AppInitMain();
     }
     catch (const std::exception& e) {
         PrintExceptionContinue(&e, "AppInit()");
@@ -175,10 +167,9 @@ bool AppInit(int argc, char* argv[])
 
     if (!fRet)
     {
-        Interrupt(threadGroup);
-        threadGroup.join_all();
+        Interrupt();
     } else {
-        WaitForShutdown(&threadGroup);
+        WaitForShutdown();
     }
     Shutdown();