CCBC-538: Fix memory leak for http requests with body

Change-Id: I446b39a7dcdca01dfea66b12ed5302be78c734b2
Reviewed-on: http://review.couchbase.org/42697
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>