Lot's of warn logs related to FreeContext

[s1monw]

I see tons of these logs when I run some tests:

[2014-05-13 12:17:52,428][WARN ][org.elasticsearch.transport.netty] [node_1] Message not fully read (response) for [91] handler org.elasticsearch.transport.EmptyTransportResponseHandler@7bfccc86, error [false], resetting
[2014-05-13 12:17:52,432][WARN ][org.elasticsearch.transport.netty] [node_2] Message not fully read (response) for [50] handler org.elasticsearch.transport.EmptyTransportResponseHandler@7bfccc86, error [false], resetting
...

I think this is related to #5730 since we now actually send a non-empty response back on freeContext.