Only use FLAG_UPDATE_CURRENT when creating PendingIntents

Using FLAG_ONE_SHOT is asking for trouble because we have no checks in
place to guarantee PendingIntents aren't reused.
Same goes for FLAG_NO_CREATE. We used this in a couple of places where
we previously created a PendingIntent for a "device action" and then
tried to reuse that PendingIntent for a "Wear action". But in some cases
only a "Wear action" was created. So creating a PendingIntent with
FLAG_NO_CREATE returned null. As a result we got notifications with
action buttons that did nothing.