Numerous changes that improve the robustness of the APR/native connector.

• addList and closeList was not protected by a sync. This could have led to corruption of these lists.
• Fix an issue where sockets could end up being closed twice if they were in the poller, the connector is stopped and then closeSocket() was called.
• When destroy() waits for the poller to exit, it needs to account for when there are multiple pollers.
• Let destroy() handle the socket close if the poller has stopped in case the socket is already in the poller for a different event.

http://svn.apache.org/r1666103
http://svn.apache.org/r1666104
http://svn.apache.org/r1666105
http://svn.apache.org/r1666106