firewall: Cleanup rules reloading.

This has been messed up a lot because there were multiple
files which indicated that a reload is needed; shell commands
were used to create and remove the indicator file; some
functions were duplicated.

src/misc-progs/forwardfwctrl.c

@@ -5,12 +5,21 @@
  *
  */
 
+#include <unistd.h>
+
 #include "setuid.h"
 
 int main(int argc, char *argv[]) {
 	if (!(initsetuid()))
 		exit(1);
 
-	safe_system("/var/ipfire/forward/bin/rules.pl");
+	int retval = safe_system("/var/ipfire/forward/bin/rules.pl");
+
+	/* If rules.pl has been successfully executed, the indicator
+	 * file is removed. */
+	if (retval == 0) {
+		unlink("/var/ipfire/forward/reread");
+	}
+
 	return 0;
 }