download: Surface bundle download errors via debug logging

This change logs the error response body at debug level.
Since the errors could contain senstive info we don't
include them in the status message. So this approach helps to
get more information about the error at debug log level which
is mostly used in a non-prod setup.

Fixes: #6609

Signed-off-by: Ashutosh Narkar <anarkar4387@gmail.com>