http_client: ensure empty socket on error

Read all pending data out of the socket on `error` event and ensure that
no `data`/`end` handlers will be invoked on `socket.destroy()`.
Otherwise following assertion happens:

    AssertionError: null == true
        at TLSSocket.socketOnData (_http_client.js:308:3)
        at TLSSocket.emit (events.js:107:17)
        at TLSSocket.Readable.read (_stream_readable.js:373:10)
        at TLSSocket.socketCloseListener (_http_client.js:229:10)
        at TLSSocket.emit (events.js:129:20)
        at TCP.close (net.js:476:12)

Fix: https://github.com/joyent/node/issues/9348
PR-URL: https://github.com/iojs/io.js/pull/1103


Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Nicu Micleușanu <micnic90@gmail.com>