XEP-0060 prohibits publishing a request that contains an item to a node that
is both 'notification-only' and 'transient' (section 7.1.3.6)
In commit 8ed872ca63 the existing pubsub publication
test was modified (to resolve a different issue) to operate on a node that's both
'notification-only' and 'transient'. This resulted in a test that should return
an error, even though the test implementation didn't expect one.
This commit explicitly verifies that publishing an item to such a node causes
an error to be returned. A new test is added that verifies that publishing an
event notification does succeed.
fc70484cf6