Pubtime in the tests

[kaiwirt]

The tests global-cache-discard-duplicate-data and global-cache-discard-duplicate-data-alt and global-cache-discard-duplicate-data-alt2 refer to the data id and the pubtime. However updates to data (same data id) also need to set the event type in the notification message to update i.e set:

rel = "http://def.wmo.int/def/rel/wnm/-/update"

in the notification message.
See wmo-im/wis2-notification-message#47

This needs to be added / considered in the tests.

[tomkralidis]

Note that WNM updated the link relations for updated and deleted data (rel=update or rel=deletion).