New disconnect strategy.

Support asynchronous disconnects by breaking the socket only, which
should cause the thread using that socket to trigger clean-up.

Upstream commit: https://github.com/square/okhttp/commit/9c302131491d05a4ca0209ef21770592c01f76fa

Bug: 18083851
(cherry picked from commit 87ed7244)

Change-Id: Ia16147cb84eb9e73af48a2771ef734fbb7baa8f5