RFR: 8239584: EventStream::close should state that stream will be stopped

[Erik Gahlin]

Hi,

Could I have a review of a fix that makes it more clear that an event 
stream is stopped when the closed method is invoked, for example at the 
of a try-with-resources block.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8239584

CSR:
https://bugs.openjdk.java.net/browse/JDK-8240311

Webrev:
http://cr.openjdk.java.net/~egahlin/8239584/

Thanks
Erik