Agent - If no allow_notify hosts are specified, allow all
Agent - If no allow_notify hosts are specified, allow all

Spelling out all the hosts that are allowed to send messages
to the Agent could get really tedious, and there are other ways of
controlling access to this service that might be smarter in a
production environment.

Change-Id: Ie6ee5cf748d7fc9d138b09d14b5be99cd22c05f4

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