res_http_websocket: Debug write lengths.

Commit 39cc28f6 attempted to fix a
test failure observed on 32 bit test agents by ensuring that a cast from
a 32 bit unsigned integer to a 64 bit unsigned integer was happening in
a predictable place. As it turns out, this did not cause test runs to
succeed.

This commit adds several redundant debug messages that print the payload
lengths of websocket frames. The idea here is that this commit will not
cause tests to succeed for the faulty test agent, but we might deduce
where the fault lies more easily this way by observing at what point the
expected value (537) changes to some ungangly huge number.

If you are wondering why something like this is being committed to the
branch, keep in mind that in commit
39cc28f6 I noted that the observed test
failures only happen when automated tests are run. Attempts to run the
tests by hand manually on the test agent result in the tests passing.

Change-Id: I14a65c19d8af40dadcdbd52348de3b0016e1ae8d