lib/ldb Remove talloc_free() that causes double-free in callbacks.

lib/ldb Remove talloc_free() that causes double-free in callbacks.

This partially reverts 0941099a, which was a little over-eager in
fixing what were presumed to be memory leaks.

It is always the callbacks responsiblity to free the ares, but if they
don't then the end of the request should handle the cleanup.
Attempting to talloc_free() here will result (as it did in the
descriptor module) in a double-free error if the callback does free
it, and no other caller of ldb_module_send_entry() has this behaviour.

Andrew Bartlett