Return EXIT_FAILURE on post-init fatal errors

It seems odd to return `EXIT_SUCCESS` when the node aborted
execution due a fatal internal error or any post-init problem
that triggers an unrequested shutdown.

e.g. blocks or coins db I/O errors, disconnect block failure,
failure during thread import (external blocks loading process
error), among others.

Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

src/bitcoind.cpp

@@ -169,7 +169,7 @@ static bool AppInit(NodeContext& node, int argc, char* argv[])
         // Set this early so that parameter interactions go to console
         InitLogging(args);
         InitParameterInteraction(args);
-        if (!AppInitBasicSetup(args)) {
+        if (!AppInitBasicSetup(args, node.exit_status)) {
             // InitError will have been called with detailed error, which ends up on console
             return false;
         }
@@ -238,6 +238,8 @@ static bool AppInit(NodeContext& node, int argc, char* argv[])
     SetSyscallSandboxPolicy(SyscallSandboxPolicy::SHUTOFF);
     if (fRet) {
         WaitForShutdown();
+    } else {
+        node.exit_status = EXIT_FAILURE;
     }
     Interrupt(node);
     Shutdown(node);
@@ -264,5 +266,5 @@ MAIN_FUNCTION
     // Connect bitcoind signal handlers
     noui_connect();
 
-    return (AppInit(node, argc, argv) ? EXIT_SUCCESS : EXIT_FAILURE);
+    return AppInit(node, argc, argv) ? node.exit_status.load() : EXIT_FAILURE;
 }