Guard clipboard overlay logging method

Currently, there's no enforcement in the clipboard logs of the fact
that the overlay can only be dismissed once per session -- e.g. if
the user taps multiple times outside the UI to get it dismiss, we
log all of those as separate events. This change guards the logs
so that we only log one dismissal per session (unguarding on a
reset).

Bug: 241548007
Test: manual
Change-Id: I4857a0344287f5f1d795ce14c8fce69b4af70c93