emulate/traffic: fix next usage

In commit b0c9de82, line 343:

self.next_conversation_id = itertools.count().next

was changed to:

self.next_conversation_id = next(itertools.count())

which is not correct, the first one is a function, the second one is a int. This patch fixed it.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13544

Signed-off-by: Joe Guo joeg@catalyst.net.nz