parser: exit with error on invalid arguments

The parser currently indicates that it exited successfully if invalid
arguments are passed to it, which makes it difficult to detect when
other tools are calling it incorrectly. This patch causes it to return
'1' indicating a failure.

Signed-off-by: Steve Beattie <steve@nxnw.org>
Acked-by: John Johansen <john.johansen@canonical.com>

parser/parser_main.c

@@ -572,7 +572,7 @@ static int process_arg(int c, char *optarg)
 		break;
 	default:
 		display_usage(progname);
-		exit(0);
+		exit(1);
 		break;
 	}