Simplify the RESTXQ caching model to prevent leakage of tmp files.

Fix a tmp file leakage into the RESTXQ code for PUTs and POSTs.

The HttpServletRequestAdapter was presuming that consumers would know how to release the cached input stream properly - never a good idea. It ought to own it's own resources and have them released as part of it's lifecycle. That way no-one can use it incorrectly! :)