Log errors on the broker side
Log errors on the broker side

So far we logged only that the command failed (the HTTP return code was
something other than 200), but not the reason. Logging the reason as
well makes post-mortem debugging easier.

Change-Id: I79980baf9c7b1c15859aa14107d802aed7e939f3
Reviewed-by: Priya Joshi <3c6cfa6f57440adfc837c4ad04483313acbc2582@morganstanley.com>

quattor/aquilon,guillaume-philippon/aquilon,quattor/aquilon,quattor/aquilon,guillaume-philippon/aquilon,guillaume-philippon/aquilon