sock: fix and add debug messages
+ return some RX buffers that were not returned before
+ slightly change the receive side so that we are less incline to run out of receive buffers (we are less aggressive at receiving message during a single "progress loop")
+ code cleanup
Tests: Add the following feature to msg_verify: deal with the case where we run out of TX buffers; check the received value to ensure we do not get corrupted messages.