CCBC-1274: cbc, fix pointer casting in HTTP callback
CCBC-1274: cbc, fix pointer casting in HTTP callback

Change-Id: Id80e72bf984fe8f1be28bda71b7640bddb20d380
Reviewed-on: http://review.couchbase.org/c/libcouchbase/+/131436
Reviewed-by: Sergey Avseyev <87f6d5e4fd3644c3c20800cde7fd3ad1569370b3@gmail.com>
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

couchbase/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,kojiromike/libcouchbase,kojiromike/libcouchbase,kojiromike/libcouchbase,kojiromike/libcouchbase,couchbase/libcouchbase