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
Change-Id: I5f5eb648f4a5f2022c63acd7c903aac88e178d9a