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/shutdown.cpp

@@ -11,6 +11,7 @@
 
 #include <logging.h>
 #include <node/interface_ui.h>
+#include <util/check.h>
 #include <util/tokenpipe.h>
 #include <warnings.h>
 
@@ -20,6 +21,8 @@
 #include <condition_variable>
 #endif
 
+static std::atomic<int>* g_exit_status{nullptr};
+
 bool AbortNode(const std::string& strMessage, bilingual_str user_message)
 {
     SetMiscWarning(Untranslated(strMessage));
@@ -28,6 +31,7 @@ bool AbortNode(const std::string& strMessage, bilingual_str user_message)
         user_message = _("A fatal internal error occurred, see debug.log for details");
     }
     InitError(user_message);
+    Assert(g_exit_status)->store(EXIT_FAILURE);
     StartShutdown();
     return false;
 }
@@ -44,8 +48,9 @@ static TokenPipeEnd g_shutdown_r;
 static TokenPipeEnd g_shutdown_w;
 #endif
 
-bool InitShutdownState()
+bool InitShutdownState(std::atomic<int>& exit_status)
 {
+    g_exit_status = &exit_status;
 #ifndef WIN32
     std::optional<TokenPipe> pipe = TokenPipe::Make();
     if (!pipe) return false;