Review request for JMC-5617: Better icon for the Threads page.

[Marcus Hirt]

Hi all,

Small change to use the old Thread Graph icon for the Threads page:

Jira: 	https://bugs.openjdk.java.net/browse/JMC-5617
Webrev:	http://cr.openjdk.java.net/~hirt/JMC-5617/webrev.0/

Kind regards,
Marcus