Change client-side error logging to debug
Change client-side error logging to debug

A client-side error (that is something akin to a 4xx HTTP response
code) is something that is common, it is not something that should
cause WARNING level log messages. This change switches to using
DEBUG so that it is easier to filter out the noisy messages.

Change-Id: I0ce0c7afa883612fd8a184b4244991f1e2a0e19d

stackforge/wsme