r2627: use the new talloc capabilities in a bunch more places in the rpc

r2627: use the new talloc capabilities in a bunch more places in the rpc
server code. This fixes a number of memory leaks I found when testing
with valgrind and smbtorture, as the cascading effect of a
talloc_free() ensures that anything derived from the top level object
is destroyed on disconnect.
(This used to be commit 76d0b8206ce64d6ff4a192979c43dddbec726d6e)