Don't broadcast NetworkAddressRequest if DeviceAnnounce just received

[cdjackson]

If we just received a DeviceAnnounce, then we know both the network and IEEE addresses for a node, so we don't need to perform this request during discovery.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.