DefaultRequestDirector should ignore IOExceptions from stale connections

The DefaultRequestDirector was letting IOExceptions from closing stale
connections affect new requests. However, it was very common to
received "SSL shutdown failed" exceptions in this case, since an SSL
"close notify" message could not be sent. Now these and other
IOExceptions are ignored so the request can continue with a new
socket.

Bug: 3317717
Change-Id: I72f6f4a8f70aacb8b4c3e93c51e9808742d1a605