ash: use a more typical form of "print four octal digits" format

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/ash.c b/shell/ash.c
index ab8ec00..b835415 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -12854,7 +12854,7 @@
 			*p = '\0';
 			puts(buf);
 		} else {
-			out1fmt("%.4o\n", mask);
+			out1fmt("%04o\n", mask);
 		}
 	} else {
 		char *modestr = *argptr;