BUG/MINOR: tools: fix parsing "us" unit for timers

Commit c20ad0d8dbd1bb5707bbfe23632415c3062e046c (BUG/MINOR: tools:  make
parse_time_err() more strict on the timer validity) broke parsing the "us"
unit in timers. It caused `parse_time_err()` to return the string "s",
which indicates an error.

Now if the "u" is followed by an "s" we properly continue processing the
time instead of immediately failing.

This fixes #1209. It must be backported to all stable versions.

(cherry picked from commit a68380524b5b47cd77f5f4a47c1441b3c5b2cf93)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit d5a8cec169845d6a54f1fc4800e6291d58aa6f36)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit fc6bea24f545cf2ff5c9b0357c2d1edd978c7c06)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/standard.c b/src/standard.c
index a14dc91..38723dd 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -2094,6 +2094,7 @@
 		if (text[1] == 's') {
 			idiv = 1000000;
 			text++;
+			break;
 		}
 		return text;
 	case 'm': /* millisecond : "ms" or minute: "m" */