Can't silence checks from events page if client name is fqdn

The selectors are getting mangled by the presence of '.' in our client names, preventing checks from being silenced directly from the events page. This fix just escapes the client name before using it in a jquery selector.

At quick glance, it looks like the checks page might have a similar issue (if a check has a character that needs escaped), but it's not an issue for us, and off the top of my head I'm not sure if any of those characters are even allowed in check names.