Improve BindingDOMRpcImplementationAdapter performance

BindingReflections return a non-shared QNameModule instance, which means
that we may end up using suboptimal lookups when comparing QNames.
Furthermore it is not the QNameModule which we need in the fastpath, but
rather QName of the input statement, hence create a cached reference of
that -- leading to minimal object allocation in the fast path.

Change-Id: I97ceb43d80c50d53d21cc66a31bfaae6ff0193e9
Signed-off-by: Robert Varga <rovarga@cisco.com>