Drop SIGSTOP/TSTP/CONT handlers, not needed anymore

Once upon a time, SIGSTOP was used to pause Finit during flashing (MTD)
of a system image.  This to prevent Finit from accidentally starting any
programs, i.e., reading from flash disk during or after upgrade.

This was quite intrusive, and has possible nasty side effects, e.g., any
process with root access sends SIGSTOP prevents TTY login.  So this patch
now removes the functionality and recommends using a dedcicated runlevel
for such critical tasks instead.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/exec.c

@@ -301,29 +301,20 @@ static int activate_console(int noclear, int nowait)
 		tcsetattr(STDIN_FILENO, TCSAFLUSH, &c);
 	}
 
-	while (!fexist(SYNC_SHUTDOWN)) {
+	if (!fexist(SYNC_SHUTDOWN)) {
 		char c;
 		static const char clr[] = "\r\e[2K";
 		static const char cup[] = "\e[A";
 		static const char msg[] = "\nPlease press Enter to activate this console.";
 
-		if (fexist(SYNC_STOPPED)) {
-			sleep(5);
-			continue;
-		}
-
 		dprint(STDERR_FILENO, clr, strlen(clr));
 		dprint(STDERR_FILENO, msg, strlen(msg));
 		while (read(STDIN_FILENO, &c, 1) == 1 && c != '\r')
 			continue;
 
-		if (fexist(SYNC_STOPPED))
-			continue;
-
 		dprint(STDERR_FILENO, clr, strlen(clr));
 		dprint(STDERR_FILENO, cup, strlen(cup));
 		ret = 1;
-		break;
 	}
 
 	/* Restore TTY */