hg: jdk10/sandbox/jdk: http-client-branch: SubscriptionBase.cancel() NOP if called multiple times

[michael.x.mcmahon at oracle.com]

Changeset: 4e3b9a10167d
Author:    michaelm
Date:      2017-10-10 16:52 +0100
URL:       http://hg.openjdk.java.net/jdk10/sandbox/jdk/rev/4e3b9a10167d

http-client-branch: SubscriptionBase.cancel() NOP if called multiple times

! src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/internal/common/SubscriptionBase.java