Every main()/exit() should return/use one of EXIT_ codes instead of magic numbers

Github-Pull: #9067
Rebased-From: 4441018d0860fce64ee74fa78da79bbb21114ca9

src/bitcoind.cpp

@@ -127,7 +127,7 @@ bool AppInit(int argc, char* argv[])
         if (fCommandLine)
         {
             fprintf(stderr, "Error: There is no RPC client functionality in bitcoind anymore. Use the bitcoin-cli utility instead.\n");
-            exit(1);
+            exit(EXIT_FAILURE);
         }
 #ifndef WIN32
         fDaemon = GetBoolArg("-daemon", false);
@@ -187,5 +187,5 @@ int main(int argc, char* argv[])
     // Connect bitcoind signal handlers
     noui_connect();
 
-    return (AppInit(argc, argv) ? 0 : 1);
+    return (AppInit(argc, argv) ? EXIT_SUCCESS : EXIT_FAILURE);
 }