notification listener: add allow_requeue param

In commit d8d2ad9 we added support for notification listener endpoint
methods to return REQUEUE, but if a driver does not support this we
raise NotImplementedError when the application attempts to requeue
a message.

This requeuing behaviour might only be used by an application in
unusual, exceptional circumstances and catch users by surprise.

Instead, let's require the application to assert that it needs this
feature in advance and raise NotImplementError at that point if the
driver doesn't support it.

Change-Id: Id0bb0e57d2dcc1ec7d752e98c9b1e8e48d99f35c
Merge "notification listener: add allow_requeue param"